Methods for maximum torque driving of robotic surgical tools

ABSTRACT

In one embodiment of the invention, a control system for a robotic surgical instrument is provided including a torque saturation limiter, a torque to current converter coupled to the torque saturation limiter, and a motor coupled to the torque to current converter. The torque saturation limiter receives a desired torque signal for one or more end effectors and limits the desired torque to a range between an upper torque limit and a lower torque limit generating a bounded torque signal. The torque to current converter transforms a torque signal into a current signal. The motor drives an end effector of one or more end effectors to the bounded torque signal in response to the first current signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This non-provisional United States (U.S.) patent application is adivisional application and claims the benefit of U.S. patent applicationSer. No. 11/535,426 filed on Sep. 26, 2006 by inventors Scott Manzo, etal., entitled MAXIMUM TORQUE DRIVING OF ROBOTIC SURGICAL TOOLS INROBOTIC SURGICAL SYSTEMS, pending. U.S. patent application Ser. No.11/535,426 claims the benefit of U.S. Provisional Patent Application No.60/817,931 filed on Jun. 29, 2006 by inventors Scott Manzo, et al.,entitled Maximum Torque Driving for Robotic Surgical Tools, now expired.

This non-provisional U.S. patent application further is related to andincorporates by reference the full disclosure of U.S. Pat. No. 6,424,885filed by Niemeyer et al. on Aug. 13, 1999, entitled “Camera ReferencedControl in a Minimally Invasive Surgical Apparatus”; U.S. Pat. No.6,594,552, filed by Nowlin et al. on Apr. 6, 2000, entitled “GripStrength with Tactile Feedback for Robotic Surgery”; U.S. Pat. No.6,840,938, filed by Morely et al. on Dec. 21, 2001, entitled “BipolarCauterizing Instrument”; U.S. Pat. No. 6,659,939, filed by Moll et al.on Nov. 3, 1999, entitled “Cooperative Minimally Invasive TelesurgicalSystem”; and U.S. Pat. No. 6,493,608, filed by Gunter D. Niemeyer onApr. 7, 1999, entitled “Aspects of a Control System of a MinimallyInvasive Surgical Apparatus”; U.S. Pat. No. 6,994,708, filed on Apr. 18,2002, by Scott Manzo entitled “Robotic Tool with MonopolarElectro-surgical Scissors”; and application Ser. Nos. 10/726,795, filedon Dec. 2, 2003, by Cooper et al. entitled “Flexible Wrist for SurgicalTool”; 10/611,411, filed on Jun. 30, 2003, by Manzo et al. entitled“Electro-surgical Instrument with Replaceable End-effectors andInhibited Surface Conduction”; 11/238,698, filed on Sep. 28, 2005, byManzo et al. entitled “Wristed Robotic Surgical Tool for PluggableEnd-effectors”; and 11/238,794, filed on Sep. 28, 2005, by Scott Manzoentitled “Wristed Robotic Tool with Replaceable End-effectorCartridges”.

FIELD

The embodiments of the invention are generally related to roboticsurgical instruments or tools and robotic surgical systems. Moreparticularly, the embodiments of the invention relate to roboticsurgical gripping tools, control systems for operating robotic surgicalgripping tools, and methods thereof for performing robotic surgicalprocedures.

BACKGROUND

Typical robotic surgical gripping instruments or tools use wires orcables to open and close jaws of the tool. With the jaws closed aroundtissue, the wires or cables may be further tensioned to generate agripping torque and apply a gripping force on the tissue. When therobotic surgical gripping instrument or tool was new, a predeterminedposition limit in a capstan or input disk is set in the tool. Thepredetermined position limit is not exceeded so that the wires or cablesin the robotic surgical gripping instrument or tool are not overloaded.

However as the robotic surgical gripping instrument or tool and itscables are used over and over again after being re-sterilized, it agesand the wires or cables that open and close jaws of the tool may stretchor the instrument may compress causing slack in the wires or cables.With stretched cables or a compressed instrument limiting the positionof the input disk to the predetermined position limit may not allow amaximum torque to be reached. This results in a reduced gripping torqueat the jaws and a reduced gripping force being applied to tissue. Thismay be particularly problematic during robotic surgical procedures.

It is desirable to provide a maximum torque to the jaws of a roboticsurgical gripping instrument or tool over its lifetime so that a maximumgripping force may be applied to tissue during robotic surgicalprocedures.

BRIEF SUMMARY

The embodiments of the invention are summarized by the claims thatfollow below.

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1 is a block diagram of a robotic surgery system to performminimally invasive robotic surgical procedures using a roboticelectro-surgical tool.

FIG. 2A is a perspective view of a robotic surgical manipulator with aplurality of robotic surgical arms at least one of which includes arobotic electro-surgical tool.

FIG. 2B is a perspective view of the robotic surgical arm including therobotic electro-surgical tool mounted thereto.

FIG. 2C illustrates mounting of the robotic electro-surgical tool to anadapter of the robotic surgical arm of FIG. 2B.

FIG. 2D illustrates a top view of the adapter of the robotic surgicalarm of FIG. 2C to which the robotic electro-surgical tool may bemounted.

FIG. 3A is a perspective view of a robotic surgical master controlconsole.

FIG. 3B is a perspective view of an exemplary gimbaled device pivotallysupporting a touch sensitive handle for the robotic surgical mastercontrol console of FIG. 3A to control robotic surgical tools including arobotic electro-surgical tool.

FIG. 3C is a cross-sectional view schematically illustrating mounting ofthe touch sensitive handle of FIG. 3B with sensors to sense gripping androtation of the handle to control robotic surgical tools, including arobotic electro-surgical tool.

FIGS. 4A-4G illustrate an exemplary robotic electro-surgical instrumentor tool with a gripping end effector.

FIGS. 5A-5B are magnified views of a distal end of the roboticelectro-surgical tool illustrated in FIG. 4A with gripping end effectorsin a closed position.

FIG. 6A illustrates a first grip with a recessed electrode.

FIG. 6B illustrates an opposing second grip with a raised electrode.

FIGS. 7A and 7B are exploded view showing the electrode, sleeve, and jawblade of the end effectors illustrated in FIGS. 5A-5B.

FIG. 8 is a schematic view of the cables and pulleys in the cable drivesystem of the robotic surgical tool and a robotic surgical arm.

FIG. 9 shows a schematic side view of the cable drive system of FIG. 8in the robotic surgical tool and the robotic surgical arm with aninterface there between.

FIG. 10 shows a three-dimensional schematic view of the cable drivesystem to the end effectors and wrist mechanism at the end of therobotic surgical tool.

FIG. 11 is a simplified schematic diagram illustrating the forcetransmission provided by a pair of jaws of the end effectors.

FIG. 12A is a top view of the surgical instrument shown in FIG. 4 with ahousing cover having been removed to show working elements inside amountable housing.

FIG. 12B is a side view of a driven element extending through the baseof the mountable housing illustrated in FIG. 12A.

FIGS. 13A-13C illustrate a variety of input disk positions to drive theend effectors.

FIGS. 14A-14C illustrate exemplary actual positions of the end effectorsrespectively corresponding to the input disk positions of FIGS. 13A-13C.

FIG. 14D illustrates a desired position of the end effectors that is notreached.

FIGS. 15A-15C illustrate exemplary positions of the master gripsrespectively corresponding to the input disk positions of FIGS. 13A-13C,the exemplary actual positions of the end effectors of FIGS. 14A-14C,and the desired position of the end effectors of FIG. 14D.

FIG. 16A schematically illustrates a high level control architecturemodel of a master/slave surgical robotic system.

FIG. 16B shows a block diagram representing control steps followed bythe control system of the minimally invasive surgical apparatus ineffecting control between master positional and orientational movementand slave end effector positional and orientational movement.

FIG. 17 is a functional block diagram schematically illustrating anenhanced grip force master/slave arrangement in which a mechanicalbiasing mechanism provides tactile feedback to the system operator.

FIGS. 18A-18B schematically illustrate simplified master/slave controlsystems to provide a maximum joint torque limit at the joint of the endeffectors.

FIG. 19 illustrates a functional block diagram of the torque saturationlimiter illustrated in FIGS. 18A-18B.

FIG. 20 graphically illustrates a function for enhancing an error signalby modifying the gain so that the master grip members can apply themaximum joint torque up to the maximum joint torque limits at the jointof the end effectors.

FIGS. 21A-21B schematically illustrate the use of the master gripmembers to apply the maximum joint torque limit to the joint at the endeffectors.

FIG. 22A graphically illustrates end effector forces.

FIG. 22B graphically illustrates master grip forces corresponding to theend effector forces illustrated in FIG. 22A.

FIG. 23 is a flow chart that illustrates an exemplary method of systemsetup with torque limited drivers for robotic surgical tools.

FIG. 24 is a flow chart that illustrates an exemplary method ofoperation of robotic surgical tools with torque limited drivers.

Note that these figures are for illustration purposes and do notnecessarily reflect the actual shape, size, or dimensions of objectsbeing illustrated.

DETAILED DESCRIPTION

In the following detailed description of the embodiments of theinvention, numerous specific details are set forth in order to provide athorough understanding of the embodiments of the invention. However, itwill be obvious to one skilled in the art that the embodiments of theinvention may be practiced without these specific details. In otherinstances well known methods, procedures, components, and circuits havenot been described in detail so as not to unnecessarily obscure aspectsof the embodiments of the invention.

Introduction

The embodiments of the invention include methods, apparatus, and systemsto drive robotic gripping and electro-surgical tools to maximum jointtorque throughout their life. A servomotor or driver is limited by amaximum torque setting so that the end effectors of a robotic surgicaltool can be driven to the maximum allowed torque. This ensures thatinput disks at the interface of the tool continue to rotate until themaximum torque setting has been attained, if so commanded by a gripinput at the master console. A grip compliance feature in the toolsoftware is adjusted by the robotic surgical tool to drive the endeffectors to their maximum torque limits.

In one embodiment of the invention, a control system for a roboticsurgical instrument is provided. The control system includes a torquesaturation limiter, a first torque to current converter coupled to thetorque saturation limiter, and a first motor coupled to the first torqueto current converter. The torque saturation limiter receives a desiredtorque signal for one or more end effectors. The torque saturationlimiter to limit the desired torque to a range between an upper torquelimit and a lower torque limit to generate a bounded torque signalrepresenting a bounded torque. The first torque transforms a torquesignal into a first current signal. The first motor drives a first endeffector of the one or more end effectors to the bounded torque inresponse to the first current signal.

In another embodiment of the invention, a robotic surgical instrument isprovided for driving end effectors to maximum torque limits. The roboticsurgical instrument includes an interface base to mechanically andelectrically couple to an end of a robotic arm, a hollow shaft coupledto the interface base, and at least one end effector coupled to thewrist member. The interface base has a memory to store an upper torquelimit and a lower torque limit for the robotic surgical instrument. Theat least one end effector can be driven to the maximum torque limits inresponse to the upper torque limit and the lower torque limit that arestored in the memory of the interface base.

In another embodiment of the invention, a method for a robotic surgicalinstrument is provided. The method includes limiting a desired torque toa range between an upper torque limit and a lower torque limit;transforming the desired torque into a first current signal; and drivinga first end effector to the limited desired torque in response to thefirst current signal.

In yet another embodiment of the invention, a method for a roboticsurgical instrument is provided. The method includes mounting therobotic surgical instrument to a robotic surgical arm; reading a memoryin the robotic surgical tool to determine a tool type and any controlsystem adjustments; adjusting a control system to drive a first endeffector to a torque in a range between an upper torque limit and alower torque limit; and driving the first end effector to the torque inthe range.

In still another embodiment of the invention, a method for a roboticsurgical system is provided. The method includes calibrating a roboticsurgical instrument coupled to a robotic surgical arm prior to a roboticsurgical procedure to determine a bumper point between a first endeffector and a second end effector; first squeezing grips of a touchsensitive handle to close the first end effector and the second endeffector around tissue; second squeezing the grips of the touchsensitive handle to apply additional torque to the first end effectorand the second end effector to apply a tip force to the tissue; andapplying a maximum torque to the first end effector and the second endeffector to apply a maximum tip force to the tissue regardless of cablestretch in the robotic surgical instrument.

Robotic Surgical Systems

Robotic surgery generally involves the use of a robot manipulator thathas multiple robotic manipulator arms. One or more of the roboticmanipulator arms often support a surgical tool which may be articulated(such as jaws, scissors, graspers, needle holders, micro dissectors,staple appliers, tackers, suction/irrigation tools, clip appliers, orthe like) or non-articulated (such as cutting blades, cautery probes,irrigators, catheters, suction orifices, or the like). One or more ofthe robotic manipulator arms are often used to support a surgical imagecapture device such as an endoscope (which may be any of a variety ofstructures such as a laparoscope, an arthroscope, a hysteroscope, or thelike), or, optionally, some other imaging modality (such as ultrasound,fluoroscopy, magnetic resonance imaging, or the like). Typically, thearms will support at least two surgical tools corresponding to the twohands of a surgeon and one image capture device.

Robotic surgery may be used to perform a wide variety of surgicalprocedures, including but not limited to open surgery, neurosurgicalprocedures (such as stereotaxy), endoscopic procedures (such aslaparoscopy, arthroscopy, thoracoscopy), and the like.

Referring now to FIG. 1, a block diagram of a robotic surgery system 100is illustrated to perform minimally invasive robotic surgical proceduresusing robotic electro-surgical tools 101A and 101C. Each of the roboticelectro-surgical tools 101A and 101C are robotic endoscopic surgicalinstrument that are manipulated by a slaved robotic manipulator andremotely controlled by control signals received from a master controlconsole. In contrast, manual endoscopic surgical instruments aredirectly controlled by hand. Robotic electro-surgical tool 101A is abipolar electro-surgical tool. Robotic electro-surgical tool 101C is amono-polar electro-surgical tool.

A user or operator O (generally a surgeon) performs a minimally invasivesurgical procedure on patient P by manipulating input devices at amaster control console 150. A computer 151 of the console 150 directsmovement of robotically controlled endoscopic surgical instruments(generally numbered 101), effecting movement of the instruments using arobotic surgical manipulator 152. The robotic surgical manipulator 152may also be referred to as robotic patient-side cart system or simply asa cart. The robotic surgical manipulator 152 has one or more roboticarms 153. Typically, the robotic surgical manipulator 152 includes atleast three robotic manipulator arms 153 supported by linkages, with acentral arm supporting an endoscopic camera and the robotic surgicalarms 153 to left and right of center supporting tissue manipulationtools and the robotic surgical tool 101A.

An assistant A may assist in pre-positioning of the robotic surgicalmanipulator 152 relative to patient P as well as swapping tools orinstruments 101 for alternative tool structures, and the like, whileviewing the internal surgical site via an assistant's display 154. Theimage of the internal surgical site shown to A by the assistant'sdisplay 154 and operator O by surgeon's console 150 is provided by oneof the surgical instruments 101 supported by the robotic surgicalmanipulator 152.

Generally, the robotic arms 153 of robotic surgical manipulator 152include a positioning portion and a driven portion. The positioningportion of the robotic surgical manipulator 152 remains in a fixedconfiguration during surgery while manipulating tissue. The drivenportion of the robotic surgical manipulator 152 is actively articulatedunder the direction of the operator O generating control signals at thesurgeon's console 150 during surgery. The actively driven portion of thearms 153 is herein referred to as an actuating portion 158. Thepositioning portion of the robotic arms 153 that are in a fixedconfiguration during surgery may be referred to as positioning linkageand/or “set-up joint” 156,156′.

To support electro-surgical robotic tools 101A, 101B, the roboticsurgical system 100 may further include one or more electrosurgicalgenerators 102A-102B. The one or more electrosurgical generators102A-102B are controlled by the master console 150 over the controlcables 109A-109B by a surgeon operating the master console.

The electrosurgical generator 102A is a bipolar generator. A pair ofwires 106A-106B couple between the bipolar electrosurgical generator102A and a bipolar electrosurgical robotic tool 101A. The pair of wirespair of wires 106A-106B may transfer the energy of the bipolarelectrosurgical generator 102A to a respective pair of end effectors ofthe bipolar electrosurgical robotic tool 101A to cauterize or sealtissue.

The electrosurgical generator 102B is a monopolar generator. A wire 107couples between the monopolar electrosurgical generator 102B and amonopolar electrosurgical robotic tool 101B. A ground wire 108 couplesbetween the monopolar electrosurgical generator 102B and patient P. Thewire 107 may transfer the energy of the monopolar electrosurgicalgenerator 102B to an end effector of the monopolar electrosurgicalrobotic tool 101B to cauterize or seal tissue.

Referring now to FIG. 2A, a perspective view of the robotic surgicalmanipulator 152 is illustrated. The robotic surgical manipulator 152 hasone or more robotic surgical arms 153. The robotic arm 153C includes anelectro-surgical robotic tool 101A coupled thereto. The robotic surgicalmanipulator 152 further includes a base 202 from which the roboticsurgical instruments 101 may be supported. More specifically, therobotic surgical instruments 101 are each supported by the positioninglinkage 156 and the actuating portion 158 of the arms 153. It should benoted that these linkage structures are here illustrated with protectivecovers 206,208 extending over much of the robotic arms. It should beunderstood that these protective covers 206,208 are optional, and may belimited in size or entirely eliminated in some embodiments to minimizethe inertia that is manipulated by the servomechanism, and to limit theoverall weight of robotic surgical manipulator 152.

Each of the robotic surgical tools 101A-101C, releasably couple to amoveable carriage 237 near an end of each robotic surgical arm. Eachmoveable carriage 237, with the robotic surgical tool mounted thereto,can be driven to translate along a linear guide formation 260 in theactuating portion 158 of the robotic surgical arms 153 in the directionof arrow 257.

The robotic surgical manipulator 152 generally has dimensions suitablefor transporting between operating rooms. It typically can fit throughstandard operating room doors and onto standard hospital elevators. Therobotic surgical manipulator 152 may have a weight and a wheel (or othertransportation) system that allows the cart to be positioned adjacent anoperating table by a single attendant. The robotic surgical manipulator152 may be sufficient stable during transport to avoid tipping, and toeasily withstand overturning moments that may be imposed at the ends ofthe robotic arms during use.

Referring now to FIG. 2B, a perspective view of the robotic surgical arm153C is illustrated including the electro-surgical robotic tool 101Amounted thereto. Each of the robotic manipulating arms 153 preferablyincludes a linkage 212 that constrains the movement of the surgical tool101 mounted thereto. More specifically, linkage 212 includes rigid linkscoupled together by rotational joints in a parallelogram arrangement sothat the robotic surgical tool 101A rotates around a point 215 in space.At the point 215, the robotic arm can pivot the robotic surgical tool101A about a pitch axis 215A and a yaw axis 215B. The pitch and yaw axesintersect at the point 215, which is aligned along a shaft 216 ofrobotic surgical tool 101A. The shaft is a rotatable hollow tube with anumber of cables of a cable drive system therein.

The robotic arm provides further degrees of freedom of movement to therobotic surgical tool 101A. Along an insertion axis 215C, parallel tothe central axis of the shaft 216 of the robotic surgical tool 101A, therobotic surgical tool 101A may slide into and out from a surgical siteas indicated by arrow 257. The robotic surgical tool 101A can alsorotate about the insertion axis 215C. As the robotic surgical tool 101Aslides along or rotates about the insertion axis 215C, the center point215 is relatively fixed with respect to the base 218. That is, theentire robotic arm is generally moved in order to maintain orre-position back to the center point 215.

The linkage 212 of the robotic arm 153 is driven by a series of motors217 therein in response to commands from a processor or computer. Themotors 217 in the robotic arm are also used to rotate and/or pivot therobotic surgical tool 101A at the point 215 around the axes 215A-215C.If a robotic surgical tool 101 further has end effectors to bearticulated or actuated, still other motors 217 in the robotic arm maybe used to do so. Additionally, the motion provided by the motors 217may be mechanically transferred to a different location such as by usingpulleys, cables, gears, links, cams, cam followers, and the like orother known means of transfer, such as pneumatics, hydraulics, orelectronics.

For endoscopic surgical procedures, the actuating portion 158 of therobotic arm 153 is often fitted with a hollow cannula 219. The shaft ortube of the robotic surgical tool 101 may be inserted into the hollowcannula 219. The cannula 219, which may be releasably coupled to therobotic arm 153, supports the shaft or tube of the robotic surgical tool101, preferably allowing the tool to rotate around the axis 215C andmove axially through the central bore of the cannula along the axis215C.

The robotic surgical tools 101 are generally sterile structures, oftenbeing sterilizable and/or being provided in hermetically sealed packagesfor use. As the robotic surgical tools 101 will be removed and replacedrepeatedly during many procedures, a tool holder could potentially beexposed to contamination if the interface directly engages the toolholder. To avoid contamination to a tool holder and possible crosscontamination between patients, an adaptor for coupling to roboticsurgical tools 101 is provided in a robotic arm of the robotic surgicalmanipulator.

Referring now to FIGS. 2C, 2D, and 4B, the mounting of the roboticsurgical tool 101A to an adapter 228 of the robotic surgical arm is nowbriefly described.

The robotic surgical arm 153 may include an adapter 228 to which theelectro-surgical robotic tool 101A or other surgical tool 101 may bemounted. FIG. 2D illustrates a front side of an exemplary adapter 228.The front side of the adaptor 128 is generally referred to as a toolside 230 and the opposite side is generally referred to as a holder side(not shown).

FIG. 4B illustrates a back side of an exemplary electro-surgical robotictool 400 as the surgical robotic tool 101A. The robotic surgical tool400 includes an exemplary mountable housing 401 including an interfacebase 412 that can be coupled to the adapter 228. The interface base 412and the adapter 228 may be electrically and mechanically coupledtogether to actuate the robotic surgical tool 400. Rotatably coupled tothe interface base 412 are one or more rotatable receiving members 418,also referred to as input disks. Each of the one or more rotatablereceiving members 418 includes a pair of pins 422A and 422B generallyreferred to as pins 422. Pin 422A is located closer to the center ofeach rotatable receive member 418 than pin 422B. The one or morerotatable receiving members 418 can mechanically couple respectively toone or more rotatable drivers 234 of the adapter 228. The roboticsurgical tool 101A may further include release levers 416 to release itfrom the adapter 228.

The interface base 412 may further include one or more electricalcontacts or pins 424 to electrically couple to electrical connector 242of the adapter 228. The interface base 412 may further include a printedcircuit board 425 and one or more integrated circuits 426 coupledthereto and to the one or more pins 424. The one or more integratedcircuits 426 may be used to identify the type of robotic surgical toolcoupled to the robotic arm, so that it may be properly controlled by themaster control console 150.

The adapter 228 includes one or more rotatable drivers 234 rotatablycoupled to a floating plate 236. The rotatable drivers 234 areresiliently mounted to the floating plate 236 by resilient radialmembers which extend into a circumferential indentation about therotatable drivers. The rotatable drivers 234 can move axially relativeto floating plate 236 by deflection of these resilient structures.

The floating plate 236 has a limited range of movement relative to thesurrounding adaptor structure normal to the major surfaces of theadaptor. Axial movement of the floating plate helps decouple therotatable drivers 234 from a robotic surgical tool 101 when its releaselevers 416 are actuated.

The one or more rotatable drivers 234 of the adapter 228 maymechanically couple to a part of the surgical tools 101. Each of therotatable drivers 234 may include one or more openings 240 to receiveprotrusions or pins 422 of rotatable receiving members 418 of therobotic surgical tools 101. The openings 240 in the rotatable drivers234 are configured to accurately align with the rotatable receivingelements 418 of the surgical tools 101.

The inner pins 422A and the outer pins 422B of the rotatable receivingelements 418 respectively align with the opening 240A and the opening240B in each rotatable driver. The pins 422A and openings 240A are atdiffering distances from the axis of rotation than the pins 422B andopenings 240B so as to ensure that rotatable drivers 234 and therotatable receiving elements 418 are not aligned 180 degrees out ofphase from their intended position. Additionally, each of the openings240 in the rotatable drivers may be slightly radially elongated so as tofittingly receive the pins in the circumferential orientation. Thisallows the pins 422 to slide radially within the openings 240 andaccommodate some axial misalignment between the tool and the adapter228, while minimizing any angular misalignment and backlash between therotatable drivers 234 and the rotatable receiving elements 418.Additionally, the interaction between pins 422 and openings 240 helpsrestrain the robotic surgical tool 101 in the engaged position with theadapter 228 until the release levers 416 along the sides of the housing401 push on the floating plate 236 axially from the interface so as torelease the tool 101.

When disposed in a first axial position (away from the tool side 230)the rotatable drivers are free to rotate without angular limitation. Theone or more rotatable drivers 234 may rotate clockwise orcounter-clockwise to further actuate the systems and tools of therobotic surgical instruments 101. However, as the rotatable drivers moveaxially toward the tool side 230, tabs (extending radially from therotatable drivers) may laterally engage detents on the floating platesso as to limit the angular rotation of the rotatable drivers about theiraxes. This limited rotation can be used to help engage the rotatabledrivers the rotating members of the tool as the pins 422 may push therotatable bodies into the limited rotation position until the pins arealigned with (and slide into) the openings 140 in the rotatable drivers.

While rotatable drivers 234 are described here, other types of driversor actuators may be provided in the adapter 228 to actuate systems ortools of the robotic surgical instruments 101. The adapter 228 furtherincludes an electrical connector 242 to electrically couple to surgicalinstruments 101.

The mounting of robotic surgical tool 101A to the adapter 228 generallyincludes inserting the tip or distal end of the shaft or hollow tube ofthe robotic surgical tool through the cannula 219 and sliding theinterface base 412 into engagement with the adapter 228, as illustratedin FIG. 2C. A lip 232 on the tool side 130 of the adaptor 128 slidablyreceives the laterally extending portions of the interface base 412 ofthe robotic surgical tool. A catch 244 of adapter 228 may latch onto theback end of the interface base 412 to hold the tool 101A in position.The protrusions or pins 422 extending from the one or more rotatablemembers 418 of the robotic surgical tool couple into the holes 240 inthe rotatable drivers 234 of the adapter 228.

The range of motion of the rotatable receiving elements 418 in therobotic surgical tool may be limited. To complete the mechanicalcoupling between the rotatable drivers of the adapter and the rotatablereceiving elements 418, the operator O at the surgical master controlconsole 150 may turn the rotatable drivers in one direction from center,turn the rotatable drivers in a second direction opposite the first, andthen return the rotatable drivers to center. Further, to ensure that thepins 422 enter openings 240 of adapter 228, the adapter 228 and tool101A mounted thereto may be moved along the axis 215C. The adapter 228and tool 101A mounted thereto may be moved to an initial position sothat the tip or distal end of the shaft or hollow tube is disposedwithin the cannula 219.

To dismount and remove the robotic surgical tool 101A, the releaselevers 416 may be squeezed pushing out on the mountable housing 401 torelease the pins 422 from the holes 240 and the catch 244 from the backend of the interface base. The mountable housing 401 is then pulled upto slide the interface base 412 up and out from the adapter 228. Themountable housing 401 is continually pulled up to remove the tip ordistal end of the shaft or hollow tube out from the cannula 219. Afterthe robotic surgical tool 101A is dismounted, another robotic surgicaltool may be mounted in its place, including a new or freshly sterilizedelectro-surgical robotic tool 400.

As previously discussed, the robotic surgical tool 101A may include oneor more integrated circuits 426 to identify the type of robotic surgicaltool coupled to the robotic arm, such that it may be properly controlledby the master control console 150. However, the robotic surgical systemmay determine whether or not the robotic surgical tool is compatible ornot, prior to its use.

The system verifies that the tool is of the type which may be used withthe robotic surgical system 100. The one or more integrated circuits 426may signal to the computer 151 in the master control console 150 dataregarding compatibility and tool-type to determine compatibility as wellas control information. One of the integrated circuits 426 may include anon-volatile memory to store and read out data regarding systemcompatibility, the tool-type and the control information. In anexemplary embodiment, the data read from the memory includes a characterstring indicating tool compatibility with the robotic surgical system100. Additionally, the data from the tool memory will often include atool-type to signal to the master control console how it is to becontrolled. In some cases, the data will also include tool calibrationinformation. The data may be provided in response to a request signalfrom the computer 151.

Tool-type data will generally indicate what kind of tool has beenattached in a tool change operation. For example, the tool-type datamight indicate that an electro-surgical robotic instrument 101A has beenmounted to the robotic arm. The tool-type data may include informationon wrist axis geometries, tool strengths, grip force, the range ofmotion of each joint, singularities in the joint motion space, themaximum force to be applied via the rotatable receiving elements 418,the tool transmission system characteristics including informationregarding the coupling of rotatable receiving elements 418 to actuationor articulation of a system within the robotic surgical instrument.

Instead of storing all of the tool-type date in the one or moreintegrated circuits 426, most of the tool-type data may optionally bestored in memory or a hard drive of the computer 151 in the roboticsurgical system 100. An identifier may be stored in the one or moreintegrated circuits 426 to signal the computer 151 to read the relevantportions of data in a look up table store in the memory or the harddrive of the computer. The tool-type data in the look-up table may beloaded into a memory of computer 151 by the manufacturer of the roboticsurgical system 100. The look-up table may be stored in a flash memory,EEPROM, or other type of non-volatile memory. As a new tool-type isprovided, the manufacturer can revise the look-up table to accommodatethe new tool-specific information. It should be recognized that the useof tools which are not compatible with the robotic surgery system, forexample, which do not have the appropriate tool-type data in aninformation table, could result in inadequate robotic control overrobotic surgical tool by the computer 151 and the operator O.

In addition to the tool-type data, tool specific information may bestored in the integrated circuit 426, such as for reconfiguring theprogramming of computer 151 to control the tool. There may becalibration information, such an offset, to correct a misalignment inthe robotic surgical tool. The calibration information may be factoredinto the overall control of the robotic surgical tool. The storing ofsuch calibration information can be used to overcome minor mechanicalinconsistencies between tools of a single type. For example, thetool-type data including the tool-specific data may be used to generateappropriate coordinate transformations and servo drive signals tomanipulate the robotic arm and rotate the rotatable drivers 234. In thiscase, the integrated circuit 426 includes the information to set up thecontrol system to drive the end effectors in the tool to have a maximumjoint torque setting so that the jaws of a robotic gripping tool or arobotic electrosurgical tool can clamp to tissue with a maximum force.

Additionally, some robotic surgical tools have a limited life span. Toollife and cumulative tool use information may also be stored on the toolmemory and used by the computer to determine if the tool is still safefor use. Total tool life may be measured by clock time, by procedure, bythe number of times the tool has been loaded onto a holder, and in otherways specific to the type of tool. Tool life data is preferably storedin the memory of the tool using an irreversible writing process.

Referring now to FIG. 3A, a perspective view of a robotic surgicalmaster control console 150 is illustrated. The master control console150 of the robotic surgical system 100 includes the computer 151, abinocular viewer 312, an arm support 314, a microphone 315, a pair ofcontrol input wrists and control input arms in a workspace 316, a speechrecognizer 317, foot pedals 318 (including foot pedals 318A-318B), and aviewing sensor 320.

The computer 151 may include one or microprocessors 302 to executeinstructions and a storage device 304 to store software with executableinstructions that may be used to generate control signals to control therobotic surgical system 100. The master control console 150 generatesthe control signals to control the electro-surgical robotic instrumentsin a surgical site.

The viewer 312 has at least one display where images of a surgical sitemay be viewed to perform minimally invasive surgery.

The arm support 314 can be used to rest the elbows or forearms of theoperator O (typically a surgeon) while gripping touch sensitive handles325 (see FIGS. 3B-3C), one in each hand, of the pair of control inputwrists 352 in the workspace 316 to generate control signals. The touchsensitive handles 325 are positioned in the workspace 316 disposedbeyond the arm support 314 and below the viewer 312.

When using the master control console, the operator O typically sits ina chair, moves his or her head into alignment with the binocular viewer312, and grips the touch sensitive handles 325 of the control inputwrists 352, one in each hand, while resting their forearms against thearm support 314. This allows the touch sensitive handles to be movedeasily in the control space 316 in both position and orientation togenerate control signals.

Additionally, the operator O can use his feet to control the foot-pedalsto change the configuration of the surgical system and generateadditional control signals to control robotic surgical instruments.

To ensure that the operator is viewing the surgical site whencontrolling the robotic surgical tools 101, the master control console150 may include the viewing sensor 320 disposed adjacent the binoculardisplay 312. When the system operator aligns his or her eyes with thebinocular eye pieces of the display 312 to view a stereoscopic image ofthe surgical worksite, the operator's head sets off the viewing sensor320 to enable the control of the robotic surgical tools 101. When theoperator's head is removed the area of the display 312, the viewingsensor 320 can disable or stop generating new control signals inresponse to movements of the touch sensitive handles in order to holdthe state of the robotic surgical tools.

The computer 151 with its microprocessors 302 interprets movements andactuation of the touch sensitive handles 325 (and other inputs from theoperator O or other personnel) to generate control signals to controlthe robotic surgical instruments 101 in the surgical worksite.

In one embodiment of the invention, the computer 151 and the viewer 312map the surgical worksite into the controller workspace 316 so it feelsand appears to the operator that the touch sensitive handles 325 areworking over surgical worksite.

Referring now to FIG. 3B, a perspective view of a control input wrist352 with a touch sensitive handle 325 is illustrated. The control inputwrist 352 is a gimbaled device that pivotally supports the touchsensitive handle 325 of the master control console 150 to generatecontrol signals that are used to control the robotic surgicalmanipulator 152 and the robotic surgical tools 101, includingelectro-surgical robotic tool 101A,101C. A pair of control input wrists352 are supported by a pair of control input arms in the workspace 316of the master control console 150.

The control input wrist 352 includes first, second, and third gimbalmembers 362, 364, and 366. The third gimbal member is rotationallymounted to a control input arm (not shown).

The touch sensitive handle 325 includes a tubular support structure 351,a first grip 350A, and a second grip 350B. The first grip and the secondgrip are supported at one end by the structure 351. The touch sensitivehandle 325 can be rotated about axis G illustrated in FIGS. 3B-3C. Thegrips 350A, 350B can be squeezed or pinched together about the tubularstructure 351. The “pinching” or grasping degree of freedom in the gripsis indicated by arrows Ha,Hb in FIG. 3B and arrows H in FIG. 3C.

The touch sensitive handle 325 is rotatably supported by the firstgimbal member 362 by means of a rotational joint 356 g. The first gimbalmember 362 is in turn, rotatably supported by the second gimbal member364 by means of the rotational joint 356 f. Similarly, the second gimbalmember 364 is rotatably supported by the third gimbal member 366 using arotational joint 356 d. In this manner, the control wrist allows thetouch sensitive handle 325 to be moved and oriented in the workspace 316using three degrees of freedom.

The movements in the gimbals of the control wrist 352 to reorient thetouch sensitive handle in space can be translated into control signalsto control the robotic surgical manipulator 152 and the robotic surgicaltools 101.

The movements in the grips 350A,350B of the touch sensitive handle 325can also be translated into control signals to control the roboticsurgical manipulator 152 and the robotic surgical tools 101. Inparticular, the squeezing motion of the master grips 350A,350B overtheir freedom of movement indicated by arrows Ha,Hb or H, may be used tocontrol the end effectors of the robotic surgical tools.

To sense the movements in the touch sensitive handle 325 and generatecontrols signals, sensors can be mounted in the handle 325 as well asthe gimbal member 362 of the control input wrist 352. Exemplary sensorsmay be a Hall effect transducer, a potentiometer, an encoder, or thelike.

Referring now to FIG. 3C, a cross-sectional view of the touch sensitivehandle 325 and gimbal member 362 of the control input wrist 352 isillustrated. FIG. 3C provides an example as to how the touch sensitivehandle 325 can be mounted to the control input wrist 352 to sense thegripping and rotation of the handle to control robotic surgical tools101.

As illustrated in FIG. 3C, the exemplary gimbal member 362 includesbeveled gears 368 a, 368 b which can couple the rotational motion of thetouch sensitive handle 325 to a roll sensor 370. The roll sensor 370 mayuse a potentiometer or encoder 370 b included in a roll motor 370 a tosense the rotation. Alternatively, a separate roll sensor, such as apotentiometer, may be directly coupled to the shaft 380 to sense therotation of the touch sensitive handle. In any case, a roll sensorsenses the roll motion of the touch sensitive handle 325 and generatescontrol signals in response thereto to control the robotic surgicaltools 101.

To sense a squeezing motion in the grips 350A,350B of the touchsensitive handle 325, a remote sensing assembly 386 may be included bythe gimbal member 362. The first and second grips 350A,350B are adaptedto be squeezed together by a hand of an operator O so as to define avariable grip separation. The grip separation may be determined as afunction of a variable grip angle with an axis or as a function of avariable grip separation distance, or the like. Alternative handleactuations, such as movement of a thumbwheel or knob may also beprovided in the handle to control the robotic surgical instruments 101.

In the exemplary embodiment, the remote sensor assembly 386 includes acircuit board 394 on which a first and a second Hall effect sensors,HE1, HE2 are mounted. A magnet 396 is disposed distally beyond thecircuit board 394 and the Hall effect sensors. A magnetic mass 398 isaxially coupled to the proximally oriented surface 390 of a push rod 84.Thus, the magnetic mass 398 moves (as shown by Arrow J) with the pushrod 384 and varies the magnetic field at the Hall effect sensors inresponse actuation of the grips 350A,350B.

To translate the squeezing action of the grips 350A,350B to the sensor386, the gimbal member 362 includes a push rod 384 within the tubularhandle structure 351. Each of the grips 350A, 350B pivot about arespective pivot 334 a, 334 b in the tubular handle structure 351.Urging links 335 a, 335 b respectively couple between the grips350A,350B and a first end of the push rod 384. The squeezing action ofthe grips 350A,350B is translated into a linear motion on the push rod384 by means of urging links 335 a,335 b as shown by arrow A in FIG. 3C.A second end of the push rod 384 couples to the sensor 386. As discussedpreviously, the magnetic mass 398 is axially coupled to the surface 390of the push rod 384 in order to sense the linear motion in the push rodand the squeezing motion of the grips 350A,350B.

A biasing mechanism such as spring 392 applies a force against thesqueezing motion of the grips to return them to full open when the gripsare released. The biasing spring 392 may be a linear or non-linearelastic device biasing against the depression of grips 350A, 350B, e.g.,a single or multiple element assembly including springs or other elasticmembers. For example, spring 392 may comprise a concentric dual springassembly whereby one spring provides a “softer” bias response as thegrips 350A, 350B are initially depressed, and a second spring provides asuperimposed “firm” bias response as the grips 350A, 350B approach afully depressed state. Such a non-linear bias may provide a pseudoforce-feedback to the operator.

It should be noted that a wide variety of alternative sensingarrangements may be used to translate the mechanical actuation of thetouch sensitive handle and control input wrist into control signals.While Hall effect sensors are included in the exemplary embodiment,alternative embodiments may include encoders, potentiometers, or avariety of alternative optical, electrical, magnetic, or other sensingstructures.

Electro Surgical Instruments

Exemplary embodiments of robotic electro surgical tools that can bemounted to a robotic arm in a robotic surgical system are now described.However, further details of robotic electro-surgical tools may bedescribed in U.S. patent Nos. with filing dates and named inventor asfollows U.S. Pat. Nos. 6,840,938, Dec. 21, 2001, Morley et al.; and6,994,708, Apr. 18, 2002, Scott Manzo; and application Ser. Nos.10/726,795, Dec. 2, 2003, Cooper et al.; 10/611,411, Jun. 30, 2003,Manzo et al.; 11/238,698, Sep. 28, 2005, Manzo et al.; and 11/238,794,Sep. 28, 2005, Scott Manzo, all of which are incorporated herein byreference.

Robotic surgical instruments 101 mounted on the robotic surgical arms153 typically include elongated shafts, with proximal and distal ends.End effectors are generally mounted on wrist-like mechanisms pivotallymounted on the distal ends of the shafts, for enabling the instruments101 to perform one or more surgical tasks. Generally, the elongateshafts of surgical instruments 101 allow the end effectors to beinserted through entry ports in a patient's body so as to access theinternal surgical site. Movement of the end effectors is generallycontrolled via master controls on the master console 150.

Electrosurgical instruments and systems, as well as methods ofperforming minimally invasive robotic surgical procedures with suchinstruments are now disclosed. The instruments of the embodiments of theinvention are capable of treating tissue with heat produced byelectrical energy while cutting, shearing, grasping, engaging, orcontacting treatment tissue. Electrosurgical instruments may apply ahigh-frequency alternating current to surrounding tissue, thereby tocause the tissue temperature to rise to the point where the tissue iscut or coagulates. Alternatively, electrosurgical instruments may applyheat to tissue by means of electrically generated heat inside theinstrument. The electrosurgical treatment may further reduce bleeding oftissue by cauterizing tissue and coagulating blood, or achieve variousother desired effects on the treatment tissue such as sealing tissuetogether. The electrosurgical treatment is carried out in a safe andeffective manner that incorporates a variety of safety features toprevent current leakage to non-target tissue so as to reduce collateraltissue damage, unwanted burning, or the like. The fact that acauterizing action is provided and the nature thereof should not beunderstood as limiting to the embodiments of the present invention.

Referring to FIGS. 4A-4E, a robotic electro-surgical tool or instrument400 is illustrated in greater detail than that of instruments 101A and101C. The robotic electro-surgical tool or instrument 400 includes amountable housing 401, an elongated shaft 416 having a proximal end anda distal end; and end effectors 414 coupled near the distal end of theshaft 416. The mountable housing 401 includes an interface or tool base412 coupled to the proximal end of the shaft 416. The mountable housing401 may further include one or more electrical connectors 474,474A-474B, a cover 472, and one or more release levers 417. At thedistal end of the shaft 416 is a mechanical wrist 402 to move the endeffectors 414.

The interface or tool base 412 can couple to the adapter 228 to whichother surgical tools may also couple so that the electrosurgical tool400 is removably connectable to the robotic surgical system. Duringsurgery, the adapter 228 is coupled to the moveable carriage 237. Thus,with the electrosurgical tool 400 mounted to the adapter 228, it cantranslate with the carriage 237 along the actuating portion of therobotic surgical arm 153.

When mounted to a robotic surgical arm 153, end effectors 414 may have aplurality of degrees of freedom of movement relative to arm 153, inaddition to actuation movement of the end effectors. As discussedpreviously, the electrosurgical tool 400 may be translated along aninsertion axis as indicated by arrow 257 in FIG. 2A. The elongated shaft416 is rotatably mounted to the base 412 for rotation about an axis 450extending longitudinally along the shaft 450 as indicated by therotational arrow A3. The wrist 402 may be a single pivot wrist, amulti-pivot wrist, a distal roll joint mechanism, or other joints orwrist-like mechanism to provide additional operational degrees offreedom to the end effector. The wrist 402 may pivot around an axis 451at a pivot point as indicated by the rotational arrow A1. The endeffectors 414A,414B may pivot together as a whole about pivot point 432as indicated by arrow A2.

The orientation of the mechanical wrist 402 is controlled throughpulleys in the tool base 412 and the wrist 402 with cables of cableloops wrapped around each being routed through the shaft 416. Therobotic system causes the pulleys in the tool base 412 to be rotated inorder to control the position of the mechanical wrist 402, and the endeffectors 414. Thus, the cable of the cable loops may also be referredto as a control cable. That is, the end effectors 414 are actuated fromthe tool base 412 through a cable loop, pulleys, and a spool similar tohow other elements of the wrist 402 are controlled. In this case, twocable loops are used to actuate the end effectors 414, one cable loopfor each.

Further details of mechanical wrists that may be applicable to themechanical wrist 402 are described in U.S. patent Nos. with filing datesand named inventor as follows U.S. Pat. Nos. 5,792,135, May 16, 1997,Madhani et al; 5, 979,900, May 16, 1997, Madhani et al; 5,807,377, May16, 1997, Madhani et al; 6,206,903, Oct. 8, 1999, Ramans; 6,312,435,Oct. 8, 1999, Wallace et al.; 6,371,952, Jun. 28, 1999, Madhani et al;6,394,998, Sep. 17, 1999, Wallace et al.; 6,676,684, Sep. 4, 2001,Morley et al.; 6,685,698, Jan. 10, 2003, Morley et al.; 6,699,235, Mar.2, 2004, Wallace et al.; 6,746,443, Jul. 27, 2000, Morley et al.; and6,817,974, Jun. 28, 2002, Cooper et al., all of which are incorporatedherein by reference.

The end effectors 414 are used in performing a surgical operation suchas cutting, shearing, grasping, engaging, or contacting tissue adjacenta surgical site. In one embodiment of the invention, the end effectors414 includes a pair of gripping jaws for clamping onto tissue.Additionally, a conductor electrically communicates with at least one ofthe end effectors to deliver electrical energy to tissue clamped by thegripping jaws.

As shown in FIG. 4B, the tool base 412 may be enclosed by a cover 472which mounts an electrical connector 474. A conductor 448 iselectrically coupled to the electrical connector 474 at one end and atleast one end effector at the opposite end.

Referring now to FIG. 4C, an insulated conductor 448 passes out from theshaft 416 to the rear of base 412 to the electrical connector 474 forconnection to the monopolar electrosurgical generator. The conductor 448communicates with at least one of the end effectors, to deliverelectrical energy to tissue from an electrosurgical generator G, such asthe monopolar generator 102B illustrated in FIG. 1. The tool base 412may further support a bipolar generator 102A by adding an extra wireconnection to the connector 474 or by adding an extra electricalconnector 474 and routing two wires to each of the two end effectors.

As discussed previously, the end effectors 414 are actuated from thetool base 412 through a cable of a cable loop, pulleys, and an actuatingspool. A cable loop CL may be considered to be a single cable routed ina loop around the drive pulley from the spool in the tool base. A cableloop may be formed by joining or splicing different segments of cabletogether. Each side of the cable loop CL may be referred to as being acable. In order to prevent slippage, a cable may be fixed to a pulley,shaft, capstan and/or tube at one point by soldering, welding, crimpingor other mechanical fixing means.

The tool base 412 includes actuating spools 434A-434C, guide pulleys435A-435B, and cable loops CL 436A-436C to form driven elements controlthe mechanical wrist 402 and the end effectors 414. The details of adriven element are discussed further below with reference to FIG. 12B.Each of the driven elements includes receiving elements or input disks(not visible in FIG. 4C) that releasably couple through an adapter to arotatable driving element that is mounted on the carriage 237 of therobotic arm assembly 153. The rotatable driving elements of the carriage237 are generally coupled to actuators (not shown), such as electricmotors or the like, to cause selective angular displacement of each inthe carriage 237. Selective actuation of the actuators is transmittedthrough the rotatable driving element on the carriage 137, to the inputdisks of the tool 400 and cause selective angular displacement of theactuating spools 434A-434C. This is described in greater detail belowwith reference to FIGS. 8-12B. Where more or fewer degrees of freedomare desired, the number of spools may be decreased or increased.

Referring now to FIG. 4G, to inhibit stretching of the cables C alongtheir lengths and along the shaft 416, elongate relatively rigidmembers, e.g., hypotube portions 33, may be used. The hypotube portions433 couple to opposed Tungsten cable portions 437, 438 at each end. Endsof the Tungsten cable portions 437, 438 are typically crimped intoopposing ends of the hypotubes as indicated by crimps 439. The hypotubes433 are typically hollow tubes having a circular cross-section. One ormore of the cables C may also include a non-conductive portion or aninsulator portion 456 coupled between hypotube portions. This may beparticularly useful for robotic electro-surgical tools and a live endeffector in isolating the current and voltages applied to tissue fromother parts of the instrument and system. Regardless of the use ofhypotube portions 433 and insulative portions 456, the cabling,hypotube, and insulative portions may be referred to as cables C of acable loop CL. Note that the cables C, at least in the region of thewrist, are typically made of metal, such as Tungsten or stainless steel,to provide sufficient strength, bendability and durability.

The cables of the cable loops 436A-434C are routed from the actuatingspools over the guide pulleys 435A-435B and through the shaft 416 todrive pulleys in the wrist 402. The tool base 412 further includes aspool 464 and a drum 462 with a cable loop coupled there-between tocontrol the rotation of the shaft 416 and the wrist 402.

A first end of the cable of each cable loop is wrapped in one directionaround the spool with the second end of the cable wrapped in an oppositedirection around the same spool. In this manner, one end of cable istaken up while the other end of the cable is released during therotation of a spool. Each spool includes a tension mechanism to avoidslack in the cable of each cable loop.

The shaft of each spool extends through the tool base 412 to itsunderside to couple to an engaging member. The engaging member canreleasably couple to a complimentary engaging member that is in turncoupled to an actuator of the surgical system, such as an electricmotor, to cause an angular displacement in the spool in response to acontrol signal from the control console.

An optional flush tube 476 may be mounted to a tool base cover 472 by aflush port 478 and the assembled base 412. The flush tube preferablyextends forward (distally) within the base 412 to communicate with theshaft 416 to permit fluids to be passed through the shaft 416 and/or topressurize the shaft 416. For example, introduction of insufflation gasduring surgery or the introduction of cleaning or sterilization gases orfluids prior and/or subsequent to surgery may be passed to the shaft 416via flush tube 476. U.S. Pat. No. 6,004,509 describes the use of fluidsand gases to maintain sterility of a surgical instrument, and isincorporated herein by reference.

Referring now to FIGS. 4D and 4E, the base cover 472 mounts anelectrical connector 474, in this case, a banana clip assembly 474 a,474 b, and 474 c, for the insulated conductor 448 to permit connectionto an electrosurgical generator. Note that the connections describedabove provide an insulated continuous electrical path from the baseconnector 474 to the end effectors 414A-414B protected from tissuecontact except at the jaw portions thereof. Energization of one or bothof the end effectors 414A-414B is controllable by the surgeon.

FIG. 4F illustrates a back side view of a portion of the roboticsurgical tool 400, some elements of which were previously discussed. Inparticular, the interface base 412 is illustrated with rotatablereceiving elements (“input disks”) 418 rotatably coupled thereto. Theinterface base 412 is used to mount the instrument 400 to a robotic armof a surgical robotic manipulator. The interface base 412 bothmechanically and electrically couples the surgical instrument 400 to arobotic arm of the surgical robotic manipulator 152. The release levers416 are located at the sides of the mountable housing and may be used torelease the robotic surgical instrument 400 from a robotic arm.

The rotatable receiving elements 418 provide a mechanical coupling tothe rotatable drivers 234 and drive motors mounted in the roboticsurgical arm 153 and the robotic surgical manipulator 152. Each of therotatable receiving elements 418 includes a pair of pins 422 extendingfrom a surface thereof. An inner pin 422A is closer to an axis ofrotation of each rotatable receiving elements 418 than an outer pin422B, which helps to ensure positive angular alignment of the rotatablereceiving elements 418. In one embodiment of the invention, therotatable receiving elements 418 are disk shaped and are also referredto herein as “input disks”.

The interface base 412 further includes an array of electricalconnecting pins 424 and one or more integrated circuits 426 coupled to aprinted circuit board 425 within the mountable housing 401. As theinterface base 412 is backward compatible to the adapter 228, it maybemechanically actuated by pre-existing driver motors found in the roboticsurgical manipulator 152. While the interface base 412 has beendescribed herein with reference to mechanical and electrical couplingelements, it should be understood that other modalities maybe used,including infrared coupling, magnetic coupling, inductive coupling, orthe like.

Referring momentarily now to FIG. 9, a schematic view of theelectrocautery surgical instrument 400 is illustrated. Theelectrocautery instrument 400 may be used to generate an electricalcurrent at a surgical site so as to burn or seal, e.g., ruptured bloodvessels.

In a monopolar electrosurgical system, the patient is earthed and avoltage is supplied to the electrode coupled to the end effector. Anelectrically conductive cable 448 extends from a plug 474 on the housing401 to the electrode at the end effector 812A,812B. This conductivecable, or cautery wire, may include a “service loop” around a joint axisat the wrist. The service loop, a single loose wrap around the joint,permits rotation of the cautery blade about the axis without placingundue stress or stretch on the wire during such rotation. It will beappreciated that, in use, the plug 474 is releasably connected to anappropriate electrical source. The plug 474 is typically a conventionalbanana-type plug. The housing 401 is typically of a non-conductiveplastics material.

It has been found that it is best to insulate the electrode at the endeffectors from the rest of the instrument 400 so as to inhibit currentleakage from the electrode to other elements in the instrument 400. Itwill be appreciated that should the distance between the electrode andthe patient be relatively great when a voltage is applied, current mayjump from the electrode to other conductive parts of the instrument. Insuch a case, current can be passed from the instrument 400 to thepatient along a path of least resistance, e.g., at the entry port of theshaft coincident with its center of rotation. This may cause unnecessaryburning at the entry port. Furthermore, the current may be passed alongthe instrument 400 to the telesurgical system in general and may bedamaging to sensitive electronics, e.g., forming part of the endoscopeand viewer arrangement.

Accordingly, the wrist mechanism 402,850 wherever possible is made ofnon conductive material. The wrist member 402,850 and the variouspulleys are typically made from non-conductive plastic, e.g.,polyethermide or ULTEM. Alternatively, a conductive wrist can besheathed in a nonconductive material.

The conductive cable 448 is typically sheathed in an insulative materialsuch as, e.g., polytetrafluoroethylene or TEFLON. The conductive cableis electrically coupled the electrode at the end effector 812A,812B. Theelectrode may be removably mountable on the end effector 812A,812B.Accordingly, a conductive seat or sleeve may be used to provide anelectrical connection to the electrode when in a mounted condition.

The shaft 416 is typically made entirely from a nonconductive material,or at least sheathed in such a material, to insulate the shaft from thepatient, in particular in the region of the port of entry coincidentwith the center of rotation. One nonconductive material for the shaftcomprises an electrical grade fiberglass/vinyl ester composite material.Alternatively, a shaft of stainless steel or carbon fiber may be coatedwith, e.g., a nylon or parylene, such as Nylon-11 or Parylene C.

The cables that extend internally along the shaft 416 typically havenon-conductive portions 456. Such non-conductive or insulative portionsare typically high strength polymer cables in the form of, e.g., aliquid crystal polymer (LCP) such as VECTRAN, a liquid crystalpolyester. The VECTRAN portions are typically crimped to opposedhypotube lengths. Opposed ends of such hypotubes are in turn typicallycrimped to tungsten cable lengths which extend to the spools in thehousing 401 and to the wrist mechanism 850, respectively.

It will be appreciated that a number of other elements of the tool mayalso be formed of an insulative material. For example, the pulleyarrangement 820,820B and the wrist member 850 coupled to the distal endof the shaft 416 may be formed of an insulative material such as, e.g.,ULTEM.

Electro-Surgical End Effectors

Referring now to FIGS. 5A-5B, 6A-6B, and 7A-7B, exemplary cauterizingend effectors are illustrated. U.S. Pat. No. 6,840,938, filed by Morelyet al. on Dec. 21, 2001 which has been incorporated by referenceillustrates additional embodiments of cauterizing end effectors orelectro-surgical end effectors.

FIGS. 5A-5B, illustrate a portion of an exemplary bipolar cauterizingtool 528. A wrist 574 is rotatably coupled to shaft 562 about the firstaxis A1. End effectors 578, 580 are rotatably coupled to the wrist 574about a second axis A2. Both the end effectors and the wrist can rotatetogether about the longitudinal axis A3 of the shaft 562. A negative andpositive electrode 582A, 582B (shown most clearly in FIGS. 6A and 6B)can be coupled to the end effectors to deliver a high frequencyelectrical energy into tissue engaged by the jaws 578, 580.

The conductive electrodes 582A, 582B can be coupled to an electric powersupply (see the bipolar generator 102A illustrated in FIG. 1) throughconductive leads 584A, 584B. In an exemplary embodiment, the conductiveleads can be run from the tool base end of the instrument, through theshaft 562, through lumens in wrist 574, and up to the electrodes 582A,582B disposed on the end effectors 578, 580. The distal portion of theconductive leads 584A, 584B can be run outside of the wrist 574 so as toallow for easy connection and disconnection of the conductive leads584A, 584B from the electrodes.

Depending on the specific configuration of the cauterizer, the endeffectors 578, 580 and drive system can be composed of a nonconductivematerial or a conductive material. In some embodiments, the electrodescan be insulated from the end effector with either a nonconductivebushing or sleeve that is composed of plastic, ceramic, TEFLON, ULTEM,or other non-conductive materials. If the electrodes are attacheddirectly to the end effectors, an insulating bushing can be disposedbetween the conductive end effectors and the electrodes so that the only“live” portion of the surgical instrument are the electrodes.

The electrodes of the present invention are preferably made of aconductive material such as aluminum, stainless steel, platinum,tungsten, gold, or the like. The electrodes can be in the form ofstrips, deposited material, inserts, or the like. In some embodiments,the jaws themselves can be the electrodes.

For the bipolar methods of the present invention, the two electrodes onthe end effectors should be at two electrical potentials and should notcome in contact with each other. Thus, in most embodiments theelectrodes are configured to have a gap between the electrodes even whenthe end effectors are in the closed configuration. As is the case withconventional electrosurgical instruments, a range of supply settings maybe used for cutting, coagulation and the like. Moreover, it should beappreciated, that the electrodes can be configured in a wide variety ofpatterns and designs.

An exemplary power supply can create a wattage up to approximatelyone-hundred-twenty (120) Watts of power for cauterizing the targettissue. The voltage used with a bipolar robotic cauterizer tool isgenerally between zero (0) volts (V) and one thousand (1000) V peak-topeak, and preferably between one-hundred (100) V and five-hundred (500)V. As long as the jaws and electrodes are both in good contact with thetissue intended to be cauterized and/or cut, there is much less chanceof voltage from the electrodes arcing to other conductive components onthe instrument (e.g., the wrist, shaft, or pulleys). It should beappreciated, however, that the voltage setting of the electrosurgicalpower generator will vary depending on the specific dimensions of theelectrodes, the tissue to be treated, and the like.

In exemplary embodiments, movement of end effectors 578, 580 areeffected through mechanical actuation of a yaw cable 586 and pitch cable588 via surgeon input devices. Actuation of the pitch cable 588 canrotate the end effectors 578, 580 about the wrist axis A1, whileactuation of the yaw cable 586 moves the jaws about axis A2, an axisthat is substantially perpendicular to axis A1, between an open andclosed position. Typically, the cables 586, 588 are directed throughlumens in the shaft and wrist body and through a conductive ornonconductive pulley assembly 590.

As shown in FIGS. 6A-7B, in one configuration the end effectors 578, 580include a jaw body 792 and a pivot body 794. Nonconductive sleeves 696can be removably coupled to jaw body 792 to attach electrodes 582A, 582Bto the end effector. As shown, the sleeves 696 include grip surfaces 698that can contact and grip the target tissue. The electrodes 582A, 582Bcan be molded inserts or a conductive material etched or deposited ontothe sleeves. The nonconductive sleeves can include a slot 700 forreceiving the jaw body 792 so as to insulate the end effectors from theconductive electrodes. In some configurations, the electrodes and gripsurfaces of the jaws can be “non-stick,” such as coated with a non-stickpolymer, e.g., TEFLON. The conductive leads can be routed throughopenings 702 in the sleeves 696 and jaw body 792 to contact theelectrodes 582A, 582B.

The sleeves 696 are preferably disposable so as to allow the physicianto replace the sleeves between each surgical procedure, if desired. Theconductive leads 584A, 584B can also be detachable from the electrodes582A, 582B so as to decouple the electrodes from the power supply.During or after the surgical procedure, the sleeves 696 and theelectrodes 582A, 582B can be removed from the jaw body 792 and replaced.Thus, different sized electrodes, a different tooth configuration on theend effectors, a different configuration of electrodes, or the like, canbe easily attached to the jaw body 792. In such arrangements, to allowfor easy detachment, the conductive leads 584A, 584B can be routedthrough a lumen in the wrist and to an unprotected path outside thewrist. In other embodiments, the jaws 578, 580, wrist 574, and pulleys590 can be composed of a nonconductive material and the electrodes canbe directly coupled to the end effectors. Consequently, non-conductivebushings can be positioned between the end effectors, and nonconductivesleeves that overly the jaw body 792 are not needed.

In exemplary arrangements, as shown most clearly in FIGS. 6A and 6B, thefirst electrode 582A will be disposed in a groove 604 on the jaw orsleeve and the second electrode 582B will be disposed on a boss 606.When the end effectors are moved to the closed position, the boss 606and groove 604 will interdigitate while still maintaining a gap betweenthe two electrodes. The boss and groove configuration has been found tocreate thin coagulation heating lines in the tissue when current isdelivered between the electrodes. The thin heating lines in the tissuemake it easy for the user to cut and separate the tissue by applying asmall amount of tension. The time of heating will depend primarily onthe size of the tissue being coagulated, the electrode configuration,the current, and the like.

It should be appreciated that the electrodes can be positioned onopposing end effector or on the same end effector. Moreover, theelectrodes do not have to be disposed within a groove or on a boss. Theelectrodes can contact the engaged tissue disposed between theelectrodes 582A, 582B and a current is applied between the spacedelectrodes to deliver a current flow to cauterize the tissue. Ifdesired, a tension force applied from the end effectors can cut thetissue along the cauterization heat lines to separate the tissue. Inthis case, the jaws can optionally include a cutting blade disposed onthe jaws to facilitate cutting of the tissue. The blade can bestationary or spring loaded and may be conductive or nonconductive.

Drive System

Referring now to FIG. 8, a simplified illustration of a drive system 800is shown to mechanically couple servomotors 802A, 802B to the endeffectors 812A,812B, respectively through a set of cables and pulleys.The drive system 800 further mechanically couples servomotor 802C tomove a joint of the wrist 850 of the robotic surgical tool throughanother set of cables and pulleys. The drive system 800 further stillmechanically couples servomotor 802D to the shaft 416 of the roboticsurgical tool through still another set of cables and pulleys.

The drive system 800 includes a tool drive portion 800A and a roboticsurgical arm portion 800B that are coupled together at an interface 810.The tool drive portion 800A corresponds to the drive system in therobotic surgical tool 400. The robotic surgical arm portion 800Bcorresponds to the drive system in the robotic surgical arm 153.

The tool drive portion 800A of the drive system 800 receives mechanicalinputs from the robotic surgical arm portion 800B through drivenelements 818A-818D, including input disks. From the driven element 818C,the tool drive portion of the drive system translates mechanical inputsfrom driven element 818C into articulation of a wrist member 850 aboutthe first axis A1. From the driven elements 818A-818B, the tool driveportion of the drive system translates mechanical inputs from the drivenelement 818A-818B into articulation of the wrist 850 about the firstaxis A2 as well as into actuation of the two element end effectors812A,812B by relative movement of the end effector elements about axisA2. From the driven element 818D, the tool drive portion of the drivesystem translates mechanical inputs from driven element 818D to effectrotation of the end effectors 812A-812B and the wrist 850 about the axisA3 of shaft 416 by rotating the shaft relative to housing 401 over alimited angle of rotation. In FIG. 8, the rotational motion of shaft 416about axis A3 is omitted in order to more easily show other elements ofthe system. Care should be taken to prevent over-rotation of the shaftthat may cause cables therein to twist into contact with each other andcreate friction between the cables.

The robotic surgical arm portion 800B of the drive system 800 includesservomotors 802A-802D that are mechanically coupled to rotatable driverpulleys 828A-828D through cable loops CL5-CL8 to transfer rotation ofthe servomotors to the rotatable driver pulleys. The servomotors802A-802D may be standard drive motors having position encoders.However, other actuators may be used, such as hydraulic actuators andpiezoelectric motors. To be used as an actuator in the present surgicalinstrument a drive mechanism should be able to provide variable andcontrollable force and position control. Capstans 804A-804D are coupledto shafts of the respective servomotors 802A-802D. A pair of ends ofeach cable loop CL5-CL8 are wrapped within a spiral groove around thecapstans 804A-804D so that one end is payed out as one end is take in. Apair of opposite ends of the cable loops CL5-CL8 are wrapped aroundopposite sides of a pulley of the rotatable driver pulleys 828A-828D.The cable loops CL5-CL8 may also move over one or more idler pulleys830-840 between the capstans 828A-828D and the rotatable driver pulleys828A-828D. Additionally, the robotic surgical tool 400 moves along acarriage 237 such that the cable loops CL5-CL8 and one or more idlerpulleys 830-840 may adjust in position to allow for the movement in therobotic surgical tool which is not shown in the simplified FIG. 8.

At the interface 810, the rotatable driver pulleys 828A-828D of therobotic surgical arm portion couple to the driven elements 818A-818D ofthe tool drive portion 800A when the robotic surgical tool 400 ismounted to the robotic surgical arm. The driven elements 818A-818Dcouple to the rotatable driver pulleys 828A-828D respectively through anadapter that is not shown in the simplified FIG. 8.

When the rotatable driver pulleys 828A-828D of the robotic surgical armportion couple to the driven elements 818A-818D of the tool driveportion 800A, the servo motor 802A can drive the driven pulley 820A andthe end effector 812A. The servo motor 802B can drive the driven pulley820B and the end effector 812B. The servo motor 802C can drive thedriven pulley 882 and yaw the wrist 850. The servo motor 802D can drivethe drum 884 and rotate the shaft to roll the wrist 850.

Referring back to the tool portion 800A of the drive system, endeffectors 812A,812B; wrist member 850, and the shaft 416 of the tool 400are driven by cable loops CL1, CL2, CL3, and CL4 arranged into anactuation scheme around a plurality of pulleys. The actuation schemeallows the actuation of a three degree-of-freedom wrist using four cableloops. Alternative actuation schemes using more or less cable loops andcables may be desirable in situations where the forces required foractuation of different motions differ greatly in magnitude. Employingcables instead of gears to control the robotic surgical tool 400minimizes the amount of friction and backlash within instrument. Thecombination of small moving masses and low friction enables instrument400 to provide force reflection to the master control computer 151 atthe master console 150 with high sensitivity.

Cable loop CL1 drives end effector 812A and includes a first cable C1Aand a second cable C1B forming two sides of the cable loop. The firstcable C1A engages the driven element 818A at one end in a firstdirection, wraps over one or more intermediate idler pulleys 870 in thewrist 850, and couples to the driven pulley 820A at a second end in afirst direction. The second cable C2A engages the driven element 818A atone end in a second direction, wraps over one or more intermediate idlerpulleys 876 in the wrist 850, and couples to the driven pulley 820A at asecond end in a second direction.

Cable loop CL2 drives end effector 812B and includes a first cable C2Aand a second cable C2B forming two sides of the cable loop. The firstcable C2A engages the driven element 818B at one end in a firstdirection, wraps over one or more intermediate idler pulleys 872 in thewrist 850, and couples to the driven pulley 820B at a second end in afirst direction. The second cable C2A engages the driven element 818B atone end in a second direction, wraps over one or more intermediate idlerpulleys 874 in the wrist 850, and couples to the driven pulley 820B at asecond end in a second direction.

Cable loop CL3 drives a pulley 882 in the wrist 850 to rotate it aboutaxis A1 and includes a first cable C3A and a second cable C3B formingtwo sides of the cable loop. The first cable C3A engages the drivenelement 818C at one end in a first direction and couples to the drivenpulley 882 at a second end in a first direction. The second cable C3Bengages the driven element 818C at one end in a second direction andcouples to the driven pulley 882 at a second end in a second direction.

Cable loop CL4 drives a drum 884 in the housing 401 that is coupled tothe shaft 416 to rotate it about axis A3. Similar to the cable loop CL3,the cable loop CL4 and includes a first cable and a second cable formingtwo sides of the cable loop that are coupled on opposite sides to eachof the drum 884 and the driven element 818D.

Referring now to FIG. 9, further details of the drive system 800 for theend effector 812A is illustrated with respect to the robotic surgicaltool 400 and the robotic surgical arm 153. FIG. 9 is an additionalschematic diagram illustrating the drive system for one of the two endeffectors. Servomotor 802A is mechanically coupled by the drive system800 to the end effector 812A through a series of cables and pulleys.

Cables C5A-C5B of the cable loop CL5 mechanically couple the servomotor802A to the rotatable driver pulley 828A in the robotic surgical arm153. The capstan 804A is coupled to the drive shaft 904A of theservomotor 802A. A pair of ends of the cable loop CL5 are wrapped withina spiral groove around the capstan 804A so that one end of the cable C5Ais payed out as one end of cable C5B is taken in and visa-versa. Thepair of ends at the opposite end of the cable loop CL5 are wrappedaround opposite sides of the pulley 928A of the rotatable driver pulley828A to match the linear direction of the cables C5A-C5B, as one istaken up the other is payed out. The cable loop CL5 may also move overone or more idler pulleys 831-832 between the capstan 804A and thepulley 928A of the rotatable driver pulley 828A. Through the cable loopCL5, capstan 804A, and pulley 928A, the rotation of the servomotor 802Ais mechanically coupled to the rotatable driver pulley 828A.

The rotatable driver pulley 828A mechanically couples to the input disk918A of the driven element 818A by means of a rotatable adapter 910A atthe interface 810.

In the robotic surgical tool 400, cables C1A-C1B of the cable loop CL1mechanically couple the driven element 818A to the driver pulley 820Aand its end effector 812A. One end of each of the cables C1A-C1B of thecable loop CL1 wrap around and couple to the actuating spool 920A of thedriven element 818A. The opposite end of each of the cables C1A-C1B ofthe cable loop CL1 wrap around opposite sides and couple to the drivenpulley 820A. The cable loop CL1 may also move over one or more idlerpulleys 870 between the input disk 918A and the pulley 820A. Through thecable loop CL1, input disk 918A, and pulley 820A, the rotation of thedriven element 818A is mechanically coupled to the pulley 820A and theend effector 812A.

Generally, rotation of the elements 818A-818D in a first directioncauses the pulleys to rotate in a first direction by pulling on a firstside of the cable loop and paying out the second side of the cable loop.Rotation of the elements 818A-818D in a second direction causes thepulleys to rotate in a second direction by pulling on the second side ofthe cable loop and paying out the first side of the cable loop.

In the tool portion 800A, the amount of rotation of the driven elements818A-818D that is transferred into rotation at the axes A1-A3 is afunction of the radius of the actuating spools (such as spool 920A) atthe driven elements, about which the cables wrap at one end, and theradius of the driven pulleys 820A,820B, 882 and drum 884 at the secondend. Actuating spools can be chosen with differing radius at the drivenelements 818A-818C to obtain more or less rotation in the driven membersgiven that the driven pulleys 820A,820B, 882 are often constrained bysize limitations at the distal end of the shaft 416 of the roboticsurgical tool. However, with larger shaft diameters the radius of thedriven pulleys 820A,820B, 882 can be increased to provide a greaterrange of motion and force. Additionally, the radius of the drivenpulleys 820A,820B, 882 may be chosen to allow the cables to properlyengage idler pulleys. For example, driven pulleys 820A-820B may havedifferent diameters in order to allow their cables to suitably engagetheir respective intermediate idler pulleys. Additionally, the radius ofidler pulleys may be chosen to keep the cables they are guiding straightbut are preferably small to minimize space requirements.

At the interface 810, the ratio of the radius of rotatable driverpulleys 828A-828D to the radius of the actuating spool of the drivenelements 818A-818D acts like a transmission. The ratio of these radiuseschange the amount of linear distance of cable that is pulled in andpayed out at the actuating spool in the robotic surgical tool from thatof the linear distance of cable that is pulled in and payed out at therotatable driver pulleys 828A-828D.

In the robotic surgical arm portion 800B, the amount of rotation of thecapstans 818A-818D at the motors 802A-802D that is transferred to therotatable driver pulleys 828A-828D is a function of the radius of thecapstans 818A-818D and the radius of the rotatable driver pulleys828A-828D. As these elements are found in the robotic surgical arm,their radius are constant for each type of tool that is mounted to therobotic surgical arm.

For the servomotors 802A-802B to drive the end effectors 812A-812B, atorque differential coupling matrix may be used to provide a translationof torque at the servomotors to the driven pulleys 802A-820B about theirrespective axis. For the servomotors 802C-802D to respectively drive thedriver pulley 882 and the drum 882, the coupling matrix is also used totranslate a torque at the servomotors to the driven pulley 882 and drum884 about their respective axis. At the end effectors 812A-812B, thetorque at the driven pulleys 802A-802B can be simply converted into alinear force at tips of the end effectors knowing the radius of thepulleys and the length of the end effectors extending beyond thepulleys. This linear force at the tips of the end effectors is oftenreferred to as a tip force which is further described with reference toFIG. 11 below.

Referring now to FIG. 10, three cable loops CL1, CL2, CL3 are used toeffect movement of the wrist mechanism 850 as previously discussed.Cable loops CL1 and CL2 are used to effect movement in the end effectors812A,812B about the pivotal connection or pin 1060. It will beappreciated that four cables may extend through the wrist-like member toeffect movement in the end effectors 812A,812B, although fewer cableswould be required for a single-finger end effector. Cable loop CL3 isused to effect movement in the wrist 850 about the pivotal connection orpin 1054.

One end of each cable C1A,C1B of the cable loop CL1 is anchored to thedrive pulley 820A to effect movement in the end effector 812A about thepivotal pin 1060. One end of each cable C2A,C2B of the cable loop CL2 isanchored to the drive pulley 820B to effect movement in the end effector812B about the pivotal pin 1060. One end of each cable C3A,C3B of thecable loop CL3 is anchored to the drive pulley 882 to effect movement inthe wrist 850 about the pivotal pin 1054.

As previously discussed, one or more idler pulleys may be used to routethe cable loops CL1, CL2 through the wrist 850 to the respective drivenpulleys 820A-820B.

The cable of the cable loop CL1 rides over an outer idler pulley 870 ofthe first pulley set and an outer idler pulley in the second pulley set1068 and into a circumferential channel in the driven pulley 802A overthe first cable portion C1A. From the driven pulley 802A, the cable ofthe cable loop CL1 exits from the circumferential channel in the drivenpulley 802A rides over an inner idler pulley in the third pulley set1070 and the inner idler pulley 876 in the fourth pulley set over thesecond cable portion C1B.

The cable of the cable loop CL2 rides over an inner idler pulley 872 ofthe first pulley set and an inner idler pulley in the second pulley set1068 and into a circumferential channel in the driven pulley 802B overthe first cable portion C2A. From the driven pulley 802B, the cable ofthe cable loop CL2 exits from the circumferential channel in the drivenpulley 802B rides over an outer idler pulley in the third pulley set1070 and the outer idler pulley 874 in the fourth pulley set over thesecond cable portion C2B.

To use the end effector 812A, when cable C1A is pulled in the directionof arrow A1, cable C1B is payed out and the end effector 812A is causedto displace angularly about the pivotal connection 1060 in the directionof arrow S1. If cable C1B is pulled in the direction of arrow A2, cableC1A is payed out and the end effector 812A is caused to displaceangularly about the pivotal connection 1060 in the direction of arrowS2.

To use the end effector 812A, when cable C2A is pulled in the directionof arrow B1, cable C2B is payed out and the end effector 812B is causedto displace angularly about the pivotal connection 1060 in the directionof arrow R1. When cable C2B is pulled in the direction of arrow B2,cable C2A is payed out and the end effector 812B is caused to displaceangularly about the pivotal connection 1060 in the direction of arrowR2.

Thus to coincidentally close the jaws of the end effectors 812A-812Btogether without any wrist movement, cable C1B is pulled in thedirection of arrow A2 and cable C2A is pulled in the direction of arrowB1 simultaneously. To coincidentally open the jaws of the end effectors812A-812B together without any wrist movement, cable C1A is pulled inthe direction of arrow A1 and cable C2B is pulled in the direction ofarrow B2 simultaneously.

Furthermore, the orientation of the end effectors 812A-812B may be movedtogether as a whole in the same direction relative to the wrist member52, as indicated by the arrows T1 and T2. In this case, cable C1A ispulled in the direction of arrow A1 and cable C2A is simultaneouslypulled in the direction of arrow B1 so as to displace both end effectors812A-812B in the direction of arrow T1. Similarly, to move the endeffectors 812A-812B in the direction of arrow T2, C1B is pulled in thedirection of arrow A2 and cable C2B is simultaneously pulled in thedirection of arrow B2.

All of the tension in the activation cables C1A,C1B,C2A,C2B, in thesurgical tool may not be transferred into a force at the tip of the endeffectors 812A, 812B due to the small sizes of the pulleys coupled tothe end effectors.

Referring now to FIG. 11, a simplified schematic diagram illustrates theforce transmission that may be provided by a pair of jaws of endeffectors 812A-812B such as a gripper to tissue. As discussedpreviously, the end effectors 812A-812B are coupled to driven pulleys820A-820B respectively and may be rotated about the axis A2. The pulleys820A-820B are respectively driven by the cable loops CL1-CL2.

T0 is the cable tension in the activation cable loop CL2 for the endeffector 812B. T1 is the cable tension in the activation cable loop CL1for the end effector 812A. R0 and R1 are the respective radii of thepulleys about which the jaws rotate of the end effector. L0 and L1 arethe respected distances from the center axis of the pulleys to the tipof the jaw. F0 and F1 are the respective forces applied at the tips ofthe jaws and are proportional to the cable tensions T0 and T1. Theratios R0/L0 and R1/L1 may reduce the respective forces F0 and F1 thatis to be generated by the tensions T0 and T1 respectively. This isbecause the ratios R0/L0 and R1/L1 may often be less than one andtypically are less than 0.5. While techniques of obtaining a mechanicaladvantage may increase the ratios at the end effectors, such as thosedescribed in U.S. Pat. No. 6,206,903 by Ramans, with any reduction intransferring the cable tension to the tip force, it is important todrive the maximum possible tension into the cables of the roboticsurgical tool.

While a particular embodiment of a drive system 800 has been described,possible changes to the configuration of pulleys, cables and motorsdescribed above will be apparent to those of skill in the art. Forexample, an alternate tool drive portion for the drive system isdescribed in U.S. Pat. No. 5,792,135, the full disclosure of which isincorporated herein by reference. The choice of the particular drivescheme employed in a particular embodiment will depend on theconstraints of the forces required to be exerted by the instrument andthe need to reduce the inertia and friction of the parts of theinstrument that move during its actuation. For example, a wide varietyof alternative drive systems might be employed, including alternativecabling arrangements, drive chains or belts, hydraulic drive systems,gear trains, rods, wire, or the like. In some of these drive systems,motion of end effectors 812A-812B about the axes may be coupled tomultiple driven elements 818. In other embodiments, there may be a oneto one correspondence between driven elements 818 and motion of an endeffector element about an axis. Still other embodiments may requirefewer (or more) driven elements to effect the desired degrees offreedom, for example, when a single element end effector is provided.Hence, manipulation of the end effector via interface 810 will generallyinvolve some reconfiguration of the robotic system during the toolchange, such as through the coupling matrix described previously.

Maximum Torque Driving of Robotic Surgical Instruments

Referring now to FIG. 12A, a top view of the tool base 412 isillustrated with cover removed to show the driven elements 818A-818D andthe cables C1A-C1B, C2A-C2B, C3A-C3B, and C4A-C4B of the respectivecable loops CL1, CL2, CL3, and CL4 shown in FIG. 8. The driven elements818A-818C each include an input disk 918A-918C and an actuation spool.

Referring now to FIG. 12B, a side view of the driven element 818A isillustrated that is also representative of the driven elements818B-818C. The driven element 818A includes the input disk 918A, a driveshaft 1210 coupled to the input disk, and the actuating spool 920Acoupled to the drive shaft. The input disk includes pins 1218 to matewith the adapter 910A of the interface. The drive shaft 1210 extends upthrough an opening in the tool base 412 into the interior of themountable housing. The actuating spool 920A includes an upper clampingpulley 1220U and a lower clamping pulley 1220L. Each of the upperclamping pulley 1220U and the lower clamping pulley 1220L have a firstclamp half 1221A and a second clamp half 1221B. A pair of fasteners 1222couples the first clamp half 1221A to the second clamp half 1221B andeach clamping pulley 1220U,1220L to the drive shaft 1210. The cable C1Bis wrapped around in a spiral groove and coupled to the upper clampingpulley 1220U. The cable C1A is wrapped around in a spiral groove andcoupled to the lower clamping pulley 1220L.

With each of their fasteners 1222 being loose, the upper clamping pulley1220U and the lower clamping pulley 1220L may turn independently of eachother about the drive shaft 1210. The upper clamping pulley 1220U andthe lower clamping pulley 1220L can be used to assist in the initialassembly of the cable loop CL1 through the robotic tool to the driverpulley 820A and the alignment of the end effector 812A. The upperclamping pulley 1220U and the lower clamping pulley 1220L can also beused to initially set and later adjust the tension in the cables C1A-C1Bof the cable loop CL1 between the driver pulley 820A and the actuatingspool 920A.

The ends of the cables C1A-C1B of the cable loop CL1 are wrapped aroundthe clamping pulleys 1220U-1220L in their respective spiral grooves sothat one end pays out while the other end is taken in and visa-versa. Ifthe input disk is rotated in the direction of arrow R1, cable C1A may betaken in as indicated by arrow TI₁ and cable C1B may be payed out asindicated by arrow PO₁. If the input disk is rotated in the oppositedirection as indicated by arrow R2, cable C1B may be taken in asindicated by arrow TI₂ and cable C1A may be payed out as indicated byarrow PO₂.

Referring now back to FIG. 12A, the driven element 818D has a differenttype of actuation spool but operates similarly so that cable C4A ofcable loop CL4 is taken in while cable C4B of the cable loop CL4 ispayed out and visa versa. An end of the cables C4A and C4B of the cableloop CL4 wrap around the drum 884 to rotate the shaft 416.

The cables C2A,C2B of the cable loop CL2 and cables C3A,C3B of the cableloop CL3 respectively ride on first and second pairs of stacked idlerpulleys 1201 in the tool base 412 before entering the shaft 416. Thecables C1A,C1B of the cable loop CL1 ride on a pair of stacked idlerpulleys 1202 in the tool base 412 before entering the shaft 416.

As discussed previously in reference to the drive system 800, the cablesC1A,C1B of the cable loop CL1 drive the end effector 812A and the cablesC2A,C2B of the cable loop CL2 drive the end effector 812B. In a typicalrobotic surgical tool 400, rotating the driven elements 818A,818B andthe respective input disks 918A,918B in opposite directions respectivelycloses the jaws or end effectors 812A,812B together as illustrated bythe arrows 1200A-1200B indicating the close rotational direction. Inputdisk 918A may be referred to as input disk six. Input disk 918B may bereferred to as input disk seven.

Referring now to FIGS. 13A-13C, FIGS. 14A-14D, and FIGS. 15A-15C, theoperation of closing the end effectors 812A-812B from an open positionto drive to maximum torque is now described. FIGS. 15A-15C illustratethe operation of the master grips 350A-350B around the touch sensitivehandle 325 in the master console 150 in the context of grip space. Thatis, the actual angular position θ^(a) _(M) of the master grips 350A-350Bis provided to the servomechanism control system (see FIGS. 18A-18B) todrive the input disks and the end effectors 812A,812B. FIGS. 13A-13Cillustrate the operation of the input disks 918A-918B in the roboticsurgical tool at the interface 810 in the context of disk space. Theinput disks 918A-918B physically rotate over angles in disk space inresponse to the servo-motors 802A-802B and the motor torque inputthereto. FIGS. 14A-14D illustrate the operation of the end effectors812A-812B in the robotic surgical tool in the context of wrist space atthe wrist 850. The desired angular position θ^(d) _(S) of the slave endeffectors 812A-812B in wrist space is derived as a function of theactual angular position θ^(a) _(M) of the master grips 350A-350B in gripspace. The desired angular position θ^(d) _(S) of the slave endeffectors 812A-812B is processed by the servomechanism control system inan attempt to make the difference between the desired angular positionθ^(d) _(S) and the actual angular position θ^(a) _(S) of the slave endeffectors 812A-812B be zero. The servomechanism control system may alsotake into account the velocity of the master grips in forming a jointtorque as is described below with reference to FIGS. 18A-18B.

Referring now to FIGS. 13A, 14A, 15A, and 20A, the master grips350A-350B are substantially open having a large positive actual angularposition θ^(a) _(M) at a point W, for example, on the curve 2002illustrated in FIG. 20A. The function f(.) as is discussed further belowand exemplary illustrated in FIG. 20A, is used to determine the desiredend effector slave angle θ^(d) _(s). The servomechanism drives the inputdisks 918A-918B to a first position 918A′-918B′ with the jaws or endeffectors 812A-812B being open as illustrated in FIG. 14A. The jaws orend effectors 812A-812B are at a first actual end effector slave angleθ^(a) _(s) which is congruent to the positive desired end effector slaveangle θ^(d) _(s). Note that as the master grips 350A-350B are closedfrom this position, the input disks 918A,918B are rotated in therespective close directions 1200A-1200B and the end effectors 812A-812Bclose in the direction of arrows S2 and R1, respectively.

Referring now to FIGS. 13B, 14B, 15B, and 20A, the master grips350A-350B are closed to a point where the end effectors 812A-812B justmake contact. The actual master angular position θ^(a) _(M) is at apoint O, zero degrees for example, on the curve 2002 illustrated in FIG.20A. The function f(.), such as that illustrated in FIG. 20A, may beused to determine the desired end effector slave angle θ^(d) _(s). Atthe position O on curve 2002, with the master angular position θ^(a)_(M) being zero degrees for example, the desired end effector slaveangle θ^(d) _(s) is zero degrees as well. The servomechanism drives theinput disks 918A-918B so they are rotated in their respective closedirections 1200A-1200B to a second position 918A″-918B″, that may bereferred to as a disk bumper position, where the jaws or end effectors812A-812B just touch together as illustrated in FIG. 14B. The jaws orend effectors 812A-812B are at a second actual end effector slave angleθ^(a) _(s) of substantially zero degrees that is congruent to thepositive desired end effector slave angle θ^(d) _(s).

With the input disks at the respective disk positions 918A″-918B″, thejaws or end effectors 812A-812B are substantially at an actual slaveangle θ^(a) _(s) of zero degrees with little to no force being appliedat tips of the end effectors when they just touch together or just touchtissue. The end effectors 812A-812B may be closed a little further ontissue S in a surgical site and then have a tip force F_(m) applied tothe tissue to cauterize or seal it together. While the jaws or endeffectors 812A-812B may not actually move much more, such that theactual end effector slave angle remains substantially the same,additional torque can be generated at the driven pulleys 820A-820B sothat the tip force Fm may be generated. Referring now to FIGS. 13C, 14C,14D, 15C, and 20A, the master grips 350A-350B are closed to asubstantially closed position. The actual master angular position θ^(a)_(M) is a negative number at a point P′, negative five degrees forexample, on the curve 2002 illustrated in FIG. 20A. The function f(.),such as that illustrated in FIG. 20A, may be used to determine thedesired end effector slave angle θ^(d) _(s). At the position P′ on curve2002, with the master angular position θ^(a) _(M) being negative fivedegrees for example, the desired end effector slave angle θ^(d) _(s) maybe negative 35 degrees for example.

A desired end effector slave angle θ^(d) _(s) that has a negative valueis theoretically illustrated in FIG. 14D by the end effectors 812A-812Bcrossing over one another. However, the end effectors 812A-812B do notactually cross over one another. Instead, the actual end effector slaveangle θ^(a) _(S) substantially differs from the desired end effectorslave angle θ^(d) _(s) as can be seen by a comparison of FIGS. 14C and14D. While the actual end effector slave angle θ^(a) _(s) remainssubstantially close to zero degrees, the torque applied at the joint ofthe end effectors 812A-812B has increased significantly. This is becausethe servomechanism continues to try and drive the end effectors812A-812B so that the actual end effector slave angle θ^(a) _(s) becomecongruent to the negative value of the desired end effector slave angleθ^(d) _(s). As the end effectors 812A-812B may not cross over oneanother, the actual end effector slave angle θ^(a) _(s) will not becomecongruent to the negative value of the desired end effector slave angleθ^(d) _(s). Thus, with the master grips at their substantially closedposition, the servomechanism continues to try and drive the endeffectors 812A-812B to the negative value of the desired end effectorslave angle θ^(d) _(s) unless it is limited by maximum torque values ora physical limitation in the cable drive system 800 of the roboticsurgical arm 153 and/or the robotic surgical tool 400.

In FIG. 13C, the input disks 918A-918B are further rotated in theirrespective close directions 1200A-1200B to a third position918A″′-918B″′ through a maximum torque angle of rotation θ_(TmaxA) andθ_(TmaxB), respectively where maximum torque is applied to the tissue Sby the servomechanism being limited to a maximum torque limit. Roboticsurgical tools may have different values of θ_(TmaxA) and θ_(TmaxB) foreach input disk 918A,918B to generate a maximum torque at the pulleys820A,820B after the tips touch. This may be due to differences in cabledrive systems and general instrument friction or the desire to apply avarying force to the tissue.

As illustrated in FIG. 14C, the jaws or end effectors 812A-812B have anactual end effector slave angle θ^(a) _(s) that remains at asubstantially zero degrees but now has a tip force Fm generated at thetip of the end effectors 812A-812B. As the instrument jaws or endeffectors 812A-812B come in contact to a common object, such as thetissue S, the input disks 918A,918B continue to rotate, applying tensionto the cables C1B and C2A of the respective cable loops CL1 and CL2, forexample, even though there is little movement of the end effectors812A-812B. The tension on the cables C1B and C2A of the respective cableloops CL1 and CL2 translates into maximum torque at the end effectors812A-812B and a tip force Fm for gripping tissue within the jaws of theend effectors 812A-812B.

The input disks 918A-918B have rotated from their second positions(which may be referred to as a disk bump position) until apre-determined maximum torque setting has been reached or the userreleases the master grip driving the input disks. Previously a maximumrotational position limit in wrist space could have limited the rotationof the input disks 918A-918B so that the maximum torque setting wouldnot be reached with stretched cables. For example, consider the functionf(.) illustrated by curve 2001 in FIG. 20A. The point P on curve 2001, amaximum rotational position limit in wrist space when the master grips350A-350B are fully closed, may not provide enough torque to drive theend effectors to a maximum joint torque.

In the embodiments of the invention, the maximum rotational positionlimit in wrist space is extended so that sufficient torque can begenerated to drive the end effectors to the maximum joint torque limits.For example, curve 2001 may be used for the function f(.) so that thepoint P′, a maximum rotational position limit in wrist space when themaster grips 350A-350B are fully closed, provides enough torque to drivethe end effectors to a maximum joint torque. The gain constant K_(p) forconverting angular distance of the grip to a portion of the desiredtorque value at the joint may additionally or alternatively be increasedto K_(p′) to saturate the torque limit sooner as the master grips350A,350B are closed rather than later to drive to maximum torquelimits. The increase in the gain constant K_(p′) is described furtherbelow with reference to FIGS. 18A-18B.

With the control system limitation being removed, the physicallimitations of the cable drive system 800 may still limit the rotationof the input disks 918A-918B in disk space. In FIG. 13C, physicallimitations of the cable drive system 800 may limit the rotation of theinput disks 918A-918B to their physically limited angles of rotationθ_(PLA) and θ_(PLB), respectively. As illustrated, the physicallylimited angles of rotation θ_(PLA) and θ_(PLB) are well beyond theexpected maximum torque angles of rotation θ_(TmaxA) and θ_(TmaxB). Theservomechanisms may drive the input disks 918A-918B so that the anglesθ_(TmaxA) and θ_(TmaxB) may go as high as θ_(PLA) and θ_(PLB), thephysical limit in the range of motion in robotic surgical tool and therobotic surgical arm. However, if driving to the maximum joint torqueand a physical limit is reached, a cable is well beyond the expectedcable stretch, up to a point where the cable should be replaced beforeit breaks. That is, over the life of the cables in the tool, whendriving to the maximum torque setting, a physical limit of the positionof the input disks should never be reached or else the tool should bereplaced or repaired.

In one embodiment of the invention it has been determined byexperimentation that after the cables have stretched, that a desired endeffector slave angle θ^(d) _(s) of negative seventy degrees in wristspace with the master grips being substantially closed, will ensure thata maximum torque at the pulleys 820A,820B will always be reached overthe life of a robotic surgical tool or instrument.

As discussed previously, the servomechanism continues to try and drivethe end effectors 812A-812B to the negative value of the desired endeffector slave angle θ^(d) _(s) when the master grips 350A-350B are attheir substantially closed position unless limited by maximum torquevalues. The servomechanism is limited by an upper torque limit (UTL) anda lower torque limit (LTL). As the joint torque is a large negativevalue when trying to reach the negative value of the desired endeffector slave angle θ^(d) _(s), the lower torque limit limits the jointtorque value generated by the servomechanism.

In one embodiment of the invention, a lower torque limit setting of 0.39Nm for the servomechanism yielded a measured tip force Fm at the tips ofend effectors 812A-812B of approximately 3.4 pounds (lbs). In anotherembodiment of the invention with a differing jaw length, a lower torquelimit setting of 0.14 Nm for the servomechanism yielded a measured tipforce of approximately 1.4 lbs. The amount of force applied to tissuemay be desirable for certain surgical procedures such as sealing tissueand vessels, and can vary between tool types.

Control System for Master/Slave Robotic Surgical Systems

FIG. 16A schematically illustrates a block diagram of a controlarchitecture 1600 for a master/slave robotic system that may be executedby the computer 151 in the master console 150. The control architecture1600 includes a bilateral controller 1605 to interface between themaster control at the master console 150 (“Master Manipulator” 1602) andthe slave control at the robotic surgical arm 153 (“Slave Manipulator”1608). The control architecture 1600 may feed forward control inputsfrom the human operator 1601 to the slave manipulator 1608 in thesurgical environment 1609 and may feed back a force as well as sensorinformation to the master manipulator 1602 and the human operator 1601.

The human operator 1601, such as a surgeon, moves an input device of amaster manipulator 1602 by applying manual or human forces f_(h) againstthe input device. One such input device are the grips 35A-350B. Encodersof master manipulator 1602 generate master encoder signals e_(m) whichare interpreted by a master input/output processor 1603 to determine themaster joint positions θ_(m) (“theta sub m”). The master joint positionsare used to generate Cartesian positions x_(m) of the input device ofthe master using a master kinematics model 1604. The Cartesian positionsx_(m) of the input device are coupled into the bilateral controller1605.

In the surgical environment 1609, the tissue structures in the surgicalworkspace can impose environmental forces f_(e) against a surgical endeffector (and possibly against other elements of the tool and/ormanipulator). The environmental forces f_(e) from the surgicalenvironment 1609 alter the position of the slave manipulator 1608, whichare read by an encoder as slave encoder values e_(s) which aretransmitted to the slave input/output processor 1607. The slaveinput/output processor 1607 interprets the slave encoder values e_(s) todetermine joint positions θ_(s). The joint positions θ_(s) are then usedto generate Cartesian slave position signals x_(s) according to theslave kinematics processing block 1606. The slave position signals x_(s)are coupled into the bilateral controller 1605.

The bilateral controller 1605 uses the input master and slave Cartesianpositions x_(m), x_(s) to generate the desired Cartesian forces to beapplied by the slave f_(s) so that the surgeon can manipulate the slavemanipulator 1608 as desired to perform a surgical procedure.Additionally, bilateral controller 1605 uses the Cartesian master andslave positions x_(m), x_(s) to generate the desired Cartesian forcefeedback f_(m) that is coupled into the master so as to provide forcefeedback to the surgeon.

In general, bilateral controller 1605 generates the slave and masterforces f_(s),f_(m) by mapping the Cartesian position of the master inthe master controller workspace with the Cartesian position of the endeffector in the surgical workspace according to a transformation.Preferably, the control system 1600 will derive the transformation inresponse to state variable signals provided from the imaging system sothat an image of the end effector in a display appears substantiallyconnected to the input device. These state variables will generallyindicate the Cartesian position of the field of view from the imagecapture device, as supplied by the slave manipulators supporting theimage capture device. Hence, coupling of the image capture manipulatorand slave end effector manipulator is beneficial for deriving thistransformation. Bilateral controller 1605 may be used to control one ormore robotic surgical arms 153 and the robotic surgical tools 400coupled thereto. Bilateral controller 1605 may also be provided withadditional input signals such as various types of sensors encoders,tachometers, and current-meters, for example.

Based generally on the difference in position between the master and theslave in the mapped workspace, bilateral controller 1605 generates aCartesian slave force f_(s) to urge the slave to follow the position ofthe master. The slave kinematics 1606 are used to interpret theCartesian slave forces f_(s) to generate joint torques τ_(s) (“tau subs”) of the slave which will result in the desired forces at the endeffector. Slave input/output processor 1607 uses these joint torques tocalculate slave motor currents i_(s), which reposition the slavemanipulator 1608 at slave position x_(e) within the surgical worksite.

The desired feedback forces from bilateral controller are similarlyinterpreted from Cartesian force on the master f_(m) based on the masterkinematics 1604 to generate master joint torques τ_(s). The master jointtorques are interpreted by the master input/output controller 1603 toprovide master motor current i_(m) to the master manipulator 1602, whichchanges the position x_(h) of the hand held input device in thesurgeon's hand.

It will be recognized that the control system 1600 illustrated in FIG.16A is a block diagram simplification. For example, the surgeon does notonly apply forces against the master input device, but also moves thehandle within the master workspace. Similarly, the motor currentsupplied to the motors of the master manipulator may not result inmovement if the surgeon maintains the position of the master controller.Nonetheless, the motor currents do result in tactile force feedback tothe surgeon based on the forces applied to the slave by the surgicalenvironment. Additionally, while Cartesian coordinate mapping ispreferred, the use of spherical, cylindrical, or other reference framesmay provide at least some of the advantages of the invention.

Referring now to FIG. 16B, the control system of the robotic surgicalsystem will now be described in greater detail. The control system inFIG. 16B is generally referenced by the reference number 1610. A feedforward control section 1675 of the control system 1610 is of interestin explaining how the slave end effectors are driven by the master. Theremaining feedback portion of the control system 1610 may be only ofinterest if a force feedback is to be applied to the master. Typically asimplified biasing feedback is utilized to provide some tactile feedbackto the operation of the system such that the feedback portion of thecontrol system 1610 may not be implemented

The master control 1650 has sensors, e.g., encoders, or potentiometers,or the like, associated therewith to enable the control system 1610 todetermine the position of the master control 1650 in joint space as itis moved from one position to a next position on a continual basisduring the course of performing a surgical procedure. In FIG. 16B,signals from these positional sensors are indicated by arrow 1614.Positional and velocity readings measured by the sensors 1687 are readby the input processing 1689 by the processor. It will be appreciatedthat since the master control 1650 includes a plurality of jointsconnecting one arm member thereof to the next, sufficient positionalsensors are provided on the master 1650 to enable the angular positionof each arm member relative to the arm member to which it is joined tobe determined thereby to enable the position and orientation of themaster frame on the master to be determined. As the angular positions ofone arm member relative to the arm member to which it is joined is readcyclically by the processor 1689 in response to movements induced on themaster control 1650 by the surgeon, the angular positions arecontinuously changing. The processor at 1689 reads these angularpositions and computes the rate at which these angular positions arechanging. Thus, the processor 1689 reads angular positions and computesthe rate of angular change, or joint velocity, on a continual basiscorresponding to the system processing cycle time, for example 1300 Hz.Joint position and joint velocity commands thus computed at 1689 arethen input to the Forward Kinematics (FKIN) controller 1691.

At the FKIN controller 1691, the positions and velocities in joint spaceare transformed into corresponding positions and velocities in Cartesianspace. The FKIN controller 1691 is a processor which typically employs aJacobian (J) matrix to accomplish this. It will be appreciated that theJacobian matrix transforms angular positions and velocities intocorresponding positions and velocities in Cartesian space by means ofconventional trigonometric relationships. Thus, corresponding positionsand velocities in Cartesian space, or Cartesian velocity and positioncommands, are computed by the FKIN controller 1691.

The velocity and the position in Cartesian space is input into a scaleand offset converter 1622. The velocity and the position in Cartesianspace may also be input into a Cartesian controller 1620 if forcefeedback is to be provided.

The minimally invasive surgical apparatus provides for a scale changebetween master control input movement and responsive slave outputmovement. Thus, a scale can be selected where, for example, a 1-inchmovement of the master control 1650 is transformed into a correspondingresponsive ⅕-inch movement on the slave. At the scale and offset step1622, the Cartesian position and velocity values are scaled inaccordance with the scale selected to perform the surgical procedure.Naturally, if a scale of 1:1 has been selected, no change in scale iseffected at 1622.

After a scale and offset step is performed at 1622, a resultant desiredslave position and desired slave velocity in Cartesian space is input toa simulated or virtual domain at 1612, as indicated by arrows 1611. Itwill be appreciated that the labeling of the block 1612 as a simulatedor virtual domain is for identification only and that the simulatedcontrol may be performed by elements outside of the functional block1612.

The steps imposed on the desired slave velocity and position in thevirtual domain 1612 are now generally described. A current slaveposition and velocity is continually monitored in the virtual orsimulated domain 1612. The desired slave position and velocity iscompared with the current slave position and velocity. Should thedesired slave position and/or velocity as input from 1622 not causetransgression of limitations, e.g., velocity and/or position and/orsingularity, and/or the like, as set in the virtual domain 1612, asimilar Cartesian slave velocity and position is output from the virtualdomain 1612 and input into an inverse scale and offset converter 1626.The similar velocity and position output in Cartesian space from thevirtual domain 1612 is indicated by arrows 1613 and corresponds withactual commands in joint space output from the virtual domain 1612 asindicated by arrows 1615.

As mentioned, the control system 1610 enables limitations to be set inthe simulation block 1612. These limitations can be chosen to conformwith mechanical system limitations or constraints and/or can be presetto correspond with environmentally-sensitive movement limitations at thesurgical site as will be described in greater detail hereinbelow. Thus,the limitations imposed in the simulated domain 1612, in one instance,can be regarded as virtual limitations corresponding with actualphysical system limitations. The limitations at the simulated domain1612 are not derived from actual slave movement but from simulated orvirtual slave movement. Thus, the slave is prevented from actuallytransgressing a limitation by simulating its movement and velocity andrestricting the simulated movement and velocity before instructing theactual slave to respond.

The resultant desired slave joint velocity and position signal from thesimulated domain 1612 are passed to a joint controller 1648. At thejoint controller 1648, the resultant or desired joint velocity andposition signal are compared with the current actual joint position andvelocity. The current actual joint position and velocity is derivedthrough the sensors 1649 on the slave 1698 after having been processedby processor 1651 to yield slave current position and velocity in jointspace.

The joint controller 1648 computes the torques desired on the slavemotors to cause the slave to follow the resultant joint position andvelocity signal taking its current actual joint position and velocityinto account. The joint torques so determined are then routed to anoutput processor 1654. The joint torques may also be coupled to afeedback processor 1652, if available.

The joint torques are typically computed, by way of example, by means ofthe formula τ_(J)=K_(p)Δθ_(p)+K_(f)Δθ_(v) where K_(p) is a springconstant, K_(v) is a damping constant, Δθ_(v) (“delta theta v”) is theerror or difference between the actual joint velocity input and thedesired velocity input to the joint controller 1648, and Δθ_(p), is theerror or difference between the actual joint position input and thedesired joint position input to the joint controller 1648.

The output processor 1654 determines the electrical currents to besupplied to the motors 1655 associated with the slave 1698 to yield thecommanded torques and causes the currents to be supplied to the motorsas indicated by arrow 1655.

As mentioned earlier, the slave indicated at 1698 is provided with aplurality of sensors. These sensors are typically operatively connectedto pivotal joints on the robotic arm 153 and at the motors driving therobotic surgical tool. One or more sensors may be operatively coupled tojoints or other elements of the robotic surgical tool or instrument 400.

These sensors are operatively linked to the processor at 1651. It willbe appreciated that these sensors determine current slave position.Should the slave 1698 be subjected to an external force great enough toinduce reactive movement on the slave 1698, the sensors will naturallydetect such movement. Such an external force could originate from avariety of sources such as when the robotic arm 153 is accidentallyknocked, or knocks into another robotic arm 153 or an endoscope arm, orthe like.

As mentioned, the joint controller 1648 computes torques desired tocause the slave 1698 to follow the master 1650. An external force on theslave 1698 which causes its current position to vary also causes thedesired slave movement to follow the master to vary. Thus a compoundedjoint torque is generated by the joint controller 1648, which torqueincludes the torque desired to move the slave to follow the master andthe torque desired to compensate for the reactive motion induced on theslave by the external force. The torque generated by the jointcontroller 1648 may be routed to the feedback processor at 1652, if aforce feedback system is to be provided.

End Effector Control for Maximizing Torque Drive

Referring now to FIG. 17, a block diagram of a master/slaveservomechanism arrangement 1700 is illustrated for the actuation of theslave end effector 1756 in response to movement of the master gripmembers 1730 of the master control console 150. It should be understoodthat the various master and slave positions θ may comprise vectors (inCartesian space, polar space, joint space, or the like) as well assimple angles or linear separations, and the kinematic chains of themaster and slave may be quite different, often even having differentdegrees of freedom. The amount of following force applied by theoperator on the slave are a function of a misalignment between aposition (and orientation) of the master input device 1730 and aposition (and orientation) of the slave end effector 1756. Themaster/slave servomechanism system 1700 relies on a biasing system 1760that interacts with the operator's hand 1762 to provide tactile feedbackto the operator with a feed forward system.

As illustrated schematically in FIG. 17, the master input device 1730defines an actual master position θ_(m) ^(a). The actual master positionθ_(m) ^(a) is transformed by a function f(.) and coupled into the slaveportion of the bilateral controller as a desired slave position θ_(s)^(d). FIG. 20 illustrates exemplary curves 2001,2002 of the functionf(.). The amount of force applied by the end effectors of the slave willvary with the difference between the desired position of the slave θ_(s)^(d) and the actual position of the slave θ_(s) ^(a), with the followingforce on the end effectors increasing with increasing misalignmentbetween the actual and desired positions, often with a proportionalrelationship.

It should be understood that the schematic representation provided inFIG. 17 of the servomechanism used to effect positional andorientational movement of the surgical end effector may appear quitedifferent in its structural embodiment. For example, a single controllermay be used to process both the master and slave signals. The controllercan calculate error signals based on the difference between the actualand desired positions in space, and will generate servomotor torquecontrolling signals based on those error signals. As the master inputcontroller and surgical end effector are moveable in a plurality oforientational and positional degrees of freedom, the calculation ofthese motor torques may involve vector coordinate transformations suchas those described in more detail in U.S. Pat. No. 6,424,885, filed Aug.13, 1999, the full disclosure of which was previously incorporated byreference.

In general, the actual configuration of the master and slave will bemeasured using potentiometers, encoders, or other position, velocity,and/or acceleration sensors affixed to rotational joints of the inputcontrol devices and slave manipulator. Position information may also beprovided by encoders and/or potentiometers affixed to the set-up joints,which may include both rotational joints and linear sliding joints(particularly for the vertical axis). A variety of alternativeconfiguration input mechanisms might be used, including stepper motors,optical configuration recognition systems (for example, using lightemitting diodes mounted to the surgical tools and a CCD/frame grabberoptical processing system coupled to the endoscope), and the like. Itshould also be understood that this direct master/slave arrangement willoften provide uniform following forces throughout the range of motion ofthe master and/or slave, regardless of whether the following forces areapplied using a system having a single degree of freedom, or a complexinput control device and slave mechanism having six degrees of freedomfor both the master and slave (optionally even including redundantdegrees of freedom for the master and/or slave to avoid singularities).

Referring now to FIGS. 17, 18A-18B, and 20, the actual master positionθ_(m) ^(a) is transformed by a function f(.) to derive the desired slaveposition θ_(s) ^(d) as discussed previously. Function f(.) takes theform θ_(s) ^(d)=f(θ_(m) ^(a)), and is preferably an invertible(monotonic) and continuous function of the actual master position. Thefunction f(.) may artificially increase (or in some cases, may decrease)the calculated error signal once the master grip separation drops belowa predetermined point O (where the end effectors touch) to increase thegrip strength (or decrease grip strength). This effectively increases(or decreases) the motor torque signals sent from the controller to themotors of the slave. Examples of when it may be desirable to decreasegrip strength include the use of low strength delicate tools in which avery small misalignment can produce the maximum following force, so thatthere would be little tactile indication of grip without decreasing theslope off.

In the embodiments of the present invention, it is desirable to increasethe grip strength below the predetermined point O (the bumper point) todrive the maximum torque to the end effectors. When the tool 400 ismounted or increased grip strength is otherwise selected by a switch,the function f(.) is shifted from curve 2001 to curve 2002, for example,so that a greater movement in the slave end effectors can be requestedthrough a larger desired slave position θ_(s) ^(d) and the maximumtorque can be applied to the slave end effectors.

Referring now again to FIGS. 17 and 20, once the separation between thegripping members drops below a predetermined bump point (arbitrarilyindicated at the origin O in FIG. 20), a small reduction in grippingmember separation θ_(m) ^(a) results in a significantly larger change inthe desired position of the slave θ_(s) ^(d). The gripping memberseparation θ_(m) ^(a) is reduced by squeezing the master grips 350A-350Btogether. Above the predetermined bumper point O, the actual masterposition and desired slave position can remain the same, therebyproviding the greatest dexterity for the system operator's control overthe end effector.

Referring now to FIGS. 20 and 21A-21B, the predetermined forceenhancement initiation point O is determined by the configuration ofhandle 325 and the biasing system 1760. Similarly, the fully closed or“slammed” configuration of the handle at point P on the curve may bedetermined by a stop of the handle 325. The lateral position(corresponding to θ_(m) ^(a)) of point O will preferably remainunchanged for a variety of different end effectors when different toolsare attached to a surgical robotic system. However, as noted above, theactual strengths and intended maximum forces of these different toolsmay be significantly different.

To allow the control system to drive to maximum joint torque, theprocessor may revise the function f(.) of the servomechanism. Thefunction f(.) may be selectively revised from curve 2001 where themaximum force position is point P to curve 2002 where the maximum forceposition is at point P′. This allows the servomechanism to adapt to thetool 400 and achieve maximum torque (essentially unlimited by position)while other tools are driven to a position and potentially never reachthe maximum torque limits. When tools are changed, the servomechanismcan adapt its control system without having to revise the mechanicalconfiguration of the master controller.

The tool 400 can make use of a memory device or other circuit withmemory (referred to herein as “tool memory”) mounted in the tool toinstruct the master controller to adapt its servomechanism to drive tomaximum torque or alternatively a switch may be used to do so. The toolmemory can also provide a signal verifying that the tool is compatiblewith that particular robotic system. The tool memory may also identifythe tool-type (whether it is a scalpel, needle grasper, jaws, scissors,clip applier, electrocartery blade, electro-surgical grippers or thelike) to the robotic system so that the robotic system can reconfigureits programming to take full advantage of the tools specializedcapabilities.

It will be recognized that a wide variety of functions f(.) may beapplied to enhance grip strength at the end effectors 812A-812B. In theexemplary embodiment illustrated by curves 2001,2002, function f(.)comprises a linear function directly connecting the maximum force/slampoint P or P′ with the predetermined force enhancement position O. Thisallows directly proportional control over the following forces of theslave, and can be substantially reproduced by a biasing system 1760 toprovide accurate tactile feedback. Alternatively, more complicatedfunctions might be used. Preferably, the function will be continuous soas to avoid “jumps” in gripping force at the end effectors. Functionf(.) will preferably be monotonic and invertible, particularly whereforce feedback is to be effected using a reciprocal master/slave system,as described above.

To accurately model the forces applied by the end effectors, it shouldbe recognized that the slave position will often be measured remotely(at the motor/sensor location), rather than at the end effector joint.Hence, the compliance of the system will reflect the compliance of aportion of the transmission system. This can be accommodated using theformula F_(s)=θ_(s) ^(d)(K_(servo)*K_(mech))/(K_(servo)+K_(mech)) whereF_(s) is the end effector gripping force, K_(servo) is the effectivespring constant of the motor, and K_(mech) is the spring constant of themechanical transmission elements. This equation of F_(s) may allow therobotic system to mimic the stiffness of a particular tool when mastergrip separation is at a minimum. Surgical tools often flex when fullysqueezed. By properly compensating for the spring constant of the motorand mechanical transmission elements, the overall servomechanism cantransition from a relationship determined from servomechanism designconsiderations (when wide open) to a surgical tool-like relationship(when clamped closed).

Referring now to FIGS. 18A-18B, simplified functional block diagrams ofservomechanisms 1800A-1800B for driving the end effectors to maximumtorque with one servomotor or two servomotors is illustrated. The signalprocessing used to provide the enhanced grip following forces at the endeffectors described above is also illustrated in greater detail in FIGS.18A-18B.

The servomechanisms 1800A-1800B each include a position derivative (PD)controller 1801, a torque saturation limiter 1812, and a torquedifferential coupler 1814,1814′ coupled together as shown. The torquedifferential coupler 1814 includes a coupling matrix that may vary withthe type of robotic surgical tool 400 that is attached to the roboticsurgical arm 153. To drive a pair of end effectors with a single motor1870, the servomechanism 1800A further includes a torque to currentconverter 1816 and a current limiter 1818 coupled together as shown. Todrive a pair of end effectors with a pair of motors 1870A-1870B, theservomechanism 1800B further includes a first torque to currentconverter 1816A and a first current limiter 1818A coupled together inseries to the motor 1870A and a second torque to current converter 1816Band a second current limiter 1818B coupled together in series to themotor 1870B.

From the master, the actual master grip separation θ_(m) ^(a) and theactual master grip velocity v_(m) ^(a) of the master grip members350A-350B are coupled into the PD controller 1801. From the slave, theactual slave separation θ_(s) ^(a) and the actual slave velocity v_(s)^(a) of the end effectors are coupled into the PD controller 1801.

One or more sensors 1866, 1868 measure the handle separation θ_(m) bysensing the distance between the master grip member 350A and the mastergrip member 350B to generate the actual master grip separation θ_(m)^(a). The one or more sensors 1866, 1868 may also measure the velocityv_(m) as the master grip members 350A-350B are squeezed closed andreleased to open to generate a measure of the actual master gripvelocity v_(m) ^(a). The handle 325 may include a stop 1864 to sense thefully closed or “slammed” configuration of the master grips 350A-350Band determine point P on a curve. The handle 325 may additionallyinclude a biasing structure 1860 to provide tactile feedback to a user.The biasing structure 1860 may include a bushing, one or more springs,etc.

The actual master grip separation θ_(m) ^(a) is processed using thefunction f(.) 1804A to provide the desired slave separation θ_(s) ^(d)as described above. The actual master grip velocity v_(m) ^(a) may alsobe modified according to the function f(.) 1804B to generate the desiredslave velocity v_(s) ^(d).

The actual slave separation θ_(s) ^(a) of the end effectors is measuredby one or more sensors 1806A, such as an encoder or potentiometer of themotor 1870. The actual slave velocity v_(s) ^(a) of the end effectorsmay also be measured by one or more sensors 1806B, such as a tachometersensing the velocity of the shaft of the motor 1870. For the two motors1870A-1870B of FIG. 18B, a plurality of sensors 1806A,1806B are used ateach motor and combined to determine the actual slave separation θ_(s)^(a) of the end effectors and the actual slave velocity v_(s) ^(a) ofthe end effectors opening and closing.

The actual slave separation θ_(s) ^(a) of the end effectors issubtracted from the desired slave separation θ_(s) ^(d) by thesubtractor or negative summer 1808A to provide a position error signale^(s). The actual slave velocity v_(s) ^(a) of the end effectors issubtracted from the desired slave velocity v_(s) ^(d) by the subtractoror negative summer 1808B to provide a velocity error signal e^(s′).

The position error signal e^(s) and velocity error signal e^(s′) arerespectively amplified by associated gain factors, K_(p′) and K_(v) bythe amplifiers 1802A-1802B. The amplified position error signalK_(p′)e^(s) and the amplified velocity error signal K_(v)e^(s′) areadded together by the summer 1810 to generate an unbounded joint torquesignal τ_(J) (“tau sub j”).

The unbounded joint torque τ_(J) generated by the PD controller can beexpressed by the equation τ_(J)=K_(p′)e^(s)+K_(v)e^(s′). To increase ordecrease grip strength and the joint torque, the gain factors K_(p′) andK_(v) of the amplifier can be varied. To drive the end effectors tomaximum torque, the gain factor K_(p) (such as for curve 2001 in FIG.20) was replaced with the increased gain factor K_(p′) (such as forcurve 2002 in FIG. 20) in one embodiment of the invention.

With the increase in the gain provided by the gain factor K_(p′) theunbounded joint torque needs to be limited to the maximum joint torquevalues. The unbounded joint torque τ_(J) is coupled into the torquesaturation limiter 1812 to generate a bounded joint torque signal τ_(J)′bounded by an upper torque limit (UTL) and a lower torque limit (LTL).

Referring now momentarily to FIG. 19, the function of the torquesaturation limiter 1812 is illustrated by a curve. If the unboundedjoint torque signal τ_(J) is below the LTL, it is clipped to the LTLlevel and output as the bounded joint torque signal τ_(J)′. If theunbounded joint torque signal τ_(J) is above the UTL, it is clipped tothe UTL level and output as the bounded joint torque signal τ_(J)′.Between the UTL and the LTL, the joint torque signal τ_(J) is passedthrough the torque saturation limiter 1812 as the bounded joint torquesignal τ_(J)′.

Referring now back to FIGS. 18A-18B, the bounded joint torque signalτ_(J)′ is output from the torque saturation limiter 1812 and coupledinto the torque differential coupler 1814,1814′.

The torque differential coupler 1814,1814′ is a coupling matrix totransform joint torque into motor torque. The torque differentialcoupler 1814,1814′ considers the drive mechanics (e.g., drive pulleys,actuating spools, etc.) of the robotic surgical arm 153 and the roboticsurgical tool 400 in transforming the joint torque signal τ_(J)′ into amotor torque signal τ_(M) so that the desired joint torque appears atthe end effectors. Thus, it is expected that the coupling matrix of thetorque differential coupler 1814,1814′ will vary over the differenttypes of robotic surgical tools being used.

For example, the coupling matrix of the torque differential coupler 1814for the one motor 1870 illustrated in FIG. 18A will be different fromthe coupling matrix of the torque differential coupler 1814′ for the twomotors 1870A-1870B illustrated in FIG. 18B. The coupling matrix of thetorque differential coupler 1814′ generates two motor torque signalsτ_(M1) and τ_(M2) for the two motors 1870A-1870B illustrated in FIG.18B. The coupling matrix of the torque differential coupler 1814generates a single motor torque signal τ_(M) for the motor 1870. Themotor torque signal τ_(M) and the two motor torque signals τ_(M1) andτ_(M2) may exceed the capabilities of the motors 1870, 1870A-1870B, ifnot for the current limiters 1818A-1818B.

Referring now to FIG. 18A, the motor torque signal τ_(M) from the torquedifferential coupler 1814 is coupled into the torque to currentconverter 1816. The torque to current converter 1816 divides the motortorque signal τ_(M) by a torque constant K_(τ) to generate a motorcurrent I_(m). The motor current I_(m) is coupled into the currentlimiter 1818.

The current limiter 1818 limits the motor current I_(m) that it receivesto a motor current I_(m)′ to a level below a maximum current limit (MCL)to avoid overheating and damaging the servomotor 1870 from excesscurrent levels. The motor current I_(m)′ is coupled to the motor 1870 toproduce a torque in its shaft and drive a rotatable driver and an endeffector by means of a cable drive system discussed previously withrespect to FIGS. 8-11.

Referring now to FIG. 18B, the motor torque signals τ_(M1) and τ_(M2)from the torque differential coupler 1814′ are respectively coupled intothe torque to current converters 1816A-1816B.

The torque to current converter 1816A divides the motor torque signalτ_(M1) by a torque constant K_(τ) to generate a motor current I_(m1).The torque to current converter 1816B divides the motor torque signalτ_(M2) by a torque constant K_(τ) to generate a motor current I_(m2).The motor current I_(m1) from the torque to current converter 1816A iscoupled into the current limiter 1818A. The motor current I_(m2) fromthe torque to current converter 1816B is coupled into the currentlimiter 1818B.

The current limiters 1818A-1818B respectively limit the motor currentsI_(m1) and I_(m2) that they receive to motor currents I_(m1)′ andI_(m2)′. below a maximum current limit (MCL) to avoid overheating anddamaging the servomotors 1870A-1870B from excess current levels.

The motor current I_(m1)′ is coupled to the motor 1870A to produce atorque in its shaft and drive a rotatable driver pulley 828A and an endeffector 812A by means of a cable drive system discussed previously withrespect to FIGS. 8-11. The bounded motor current I_(m2)′ is coupled tothe motor 1870B to produce a torque in its shaft and drive a rotatabledriver 828B and an end effector 812B by means of a cable drive systemdiscussed previously with respect to FIGS. 8-11. In this manner twomotors are energized to provide following grip forces for each endeffector 812A,812B.

As noted previously, FIGS. 18A-18B are simplified block diagrams of theservomechanism control systems for two differing types of roboticsurgical tools. The functional blocks of the control systems may beimplemented by software routines executing in the computer system 151 ofthe master console. The signals in this case may be digital signals orvectors that may eventually be converted into analog signals by adigital to analog converter (DAC) such as at the motors. Exemplarysoftware subroutines to execute the functions of the functional blocksof the control systems are described in detail in and shown by FIGS.13A-13C of U.S. Pat. No. 6,594,552, entitled “Grip Strength with TactileFeedback for Robotic Surgery”, filed by Nowlin et al on Apr. 6, 2000which has been previously incorporated by reference.

The control systems 1800A-1800B use velocity and velocity error signalswhich may help inhibit excessive cycling of the system as the slaveattempts to follow the master. Hence, these velocity signals represent aviscosity of the system. However, their use may not be necessary,particularly for effecting grip, in light of the small masses and highfriction and grip forces that are involved.

Furthermore, while position and velocity error signals were used tocompute an unbounded joint torque to compare against upper and lowerlimits, the use of a torque or force sensor at the motors or the endeffectors of the slave mechanism may better enable the measurement, andhence control, of the force applied by the slave to tissue.Additionally, the use of force sensor at the grip element of the mastermanipulator may enable the measurement, and hence command to the slave,of the force being applied by the operator on the handle.

Methods of Operation for Maximum Torque Drive

The robotic surgical tool is operated to ensure that a consistentgripping force is attained throughout life of instrument by driving itsend effectors to maximum torque limits instead of positional limits.

The end effectors 812A-812B of the electro surgical instrument 400 maybe controlled by the operator O seated at the robotic surgical mastercontrol console 150 in a number of ways. Typically a gripping orsqueezing motion (“master grip”) on the master grips 350A-350B of thetouch sensitive handle 325 by an operators hand 62 may be used to closethe jaws or end effectors 812A-812B of the robotic surgical instruments400 around tissue. Upon release of the master grips 350A-350B of thetouch sensitive handle 325, the jaws or end effectors 812A-812B open upand reduce the force applied to tissue.

FIG. 21A illustrates end effectors 812A-812B just engaging a suture Sbut not yet applying significant forces against the suture. As thecross-sectional thickness of suture S is quite small, the separationbetween the end effector elements is effectively zero. As no forces arebeing imposed by the servomechanism, the grip separation angle of handle325 is also substantially equal to zero. Note that the grip elementsneed not exactly define a zero angle. At this nominal position, gripelements 350A and 350B are just beginning to engage a biasing mechanism1860A of a biasing system 1860. Biasing mechanism 1860A is hereillustrated as an elastomeric bushing surrounding a grip return spring1860B. A variety of biasing structures might be used in place of biasingmechanism 1860A, including springs, magnets, or the like. The biasingmechanism may define a predetermined biasing transition point.

Referring now FIG. 22A, the force F_(master) applied to the masterincreases at a predetermined master separation point O′. This biasingsystem transition point will preferably occur just as the end effectorelements touch, and will thereby indicate to the operator the enhancedgrip strength being applied by the servomechanism.

Referring now to FIG. 22B, the end effector grip force F_(slave) isillustrated for the corresponding grip actuation by the master asillustrated in FIG. 22A, when gripping an object of negligiblethickness. Initially there is little end effector grip force F_(slave)up until the bump point O where the end effector grip force F_(slave)increases in response to the slave demand generated by the master.

Referring now to FIG. 21B, an operator's hand 2162 can squeeze handle325 beyond the nominal zero angle by compressing bushing 1860A betweenthe grip members. Once the operator squeezes the handle sufficiently toengage stops 1864 of the grip members, end effectors 812A-812B willpreferably be imposing the maximum joint torque at the end effectors andthe maximum following force F_(m) against suture S. This maximumgripping force configuration is designated by the point P′ alongfunction f(.) illustrated by the curves 2002 in FIG. 20A.Advantageously, the reactive forces provided by bushing 1860A againstoperator's hand 2162 provide tactile feedback to the operator of theenhanced following forces below the predetermined position O. Asdescribed above, function f(.) preferably comprises the identityfunction above the predetermined position O. It should be understoodthat the predetermined position O need not define any actual dimensionsor forces.

Referring now to FIG. 23, a flow chart of robotic surgical system setupfor a robotic surgical instrument to drive its end effectors to maximumtorque limits is illustrated. The method of system setup begins at thestart 2300.

At block 2302, the robotic surgical instrument or tool 400 is mounted toa robotic surgical arm 153. The method then goes to block 2304.

At block 2304, a memory in the robotic surgical instrument or tool 400is read out to determine the tool type and to determine if any controlsystem adjustments are to be made to control the cable drive system. Thememory may include the upper torque limit and the lower torque limitsettings or the tool type may provide an address to the system forlooking up the maximum torque limits. The memory may include informationregarding the coupling table that is used to transform torque intocurrent or provide an address to the system to where the information inthe coupling table can be found. After reading the memory, the methodthen goes to block 2306.

At block 2306, the control system of the robotic surgical system isadjusted to drive a first end effector to a torque in a range between anupper torque limit and a lower torque limit in the case of a single endeffector. In the case of two end effectors, the control system may beadjusted to concurrently drive a first end effector and a second endeffector to a torque in the range between the upper torque limit and thelower torque limit. In any case, the torque may be a desired jointtorque at the pivot pin of the first end effector and the second endeffector. An unbounded desired joint torque at the end effectors isbounded to drive servomotors between maximum torque settings. Theequation used to generate the unbounded desired torque value is adjustedto saturate more quickly when the touch sensitive grips of the masterconsole are squeezed more tightly around tissue. After the controlsystem adjustments are completed, the method then goes to block 2308.

At block 2308, the robotic surgical instrument or tool 400 is operatedby the robotic surgical arm 153. In the case of a single end effector,the first end effector is driven to the torque in the range limited bythe upper torque limit and the lower torque limit. The drive pulley towhich the end effector is attached is driven to the torque in thelimited range of torque. In the case of two end effectors, the first endeffector and the second end effector are concurrently driven to thetorque in the limited range. The drive pulleys to which the endeffectors are attached are driven to the torque in the limited range oftorque.

After the end effectors are driven and the robotic surgical procedure iscompleted, the method goes to block 2399 and ends.

During surgical procedures, such as when sealing vessels, the maximumgripping force at the jaws of the end effectors (torque at the inputdisks) should be achievable throughout the life of an instrument toensure consistent vessel sealing by adjusting the controls system todrive to maximum torque levels regardless of cable stretch. Driving tomaximum torque levels assures that tissue is clamped with a high gripforce for various surgical procedures. One such procedure may be to sealtissue closed. In this case, a bipolar electrosurgical robotic tool maybe used with a bipolar generator. The maximum torque levels may beautomatically set by the mounting of the tool to a robotic surgical armor they may be selectively set by an independent switch such as a pushbutton switch or a dependent switch such that the higher grip forces areactivated with the bipolar generator.

Referring now to the flow chart of FIG. 24, an exemplary operation ofthe robotic surgical system with the capability of driving end effectorsto maximum torque is now described. The method starts at block 2400 andgoes to block 2402.

At block 2402, the robotic surgical instrument coupled to the roboticsurgical arm is calibrated prior to a robotic surgical procedure. Duringsuch calibration or initialization, a pair of end effectors may bedriven to determine a bump point. The bump point is the position of theinput disks where a first end effector and a second end effector justclose together and touch each other with substantially zero force. Thisis the point where the torque is applied to apply a force at the tips ofthe end effectors. After calibration, the method goes to block 2404.

At block 2404, the grips of the touch sensitive handle are firstsqueezed to close the first end effector and the second end effectoraround tissue without applying significant force to the tissue. Afterclosing around the tissue the method goes to block 2406.

At block 2406, the grips of the touch sensitive handle are squeezedfurther to apply additional torque to the first end effector and thesecond end effector to apply a tip force to the tissue. If a vessel, thevessel may begin to close by the tip force. After starting to apply thetip force, the method goes to block 2408.

At block 2408, the maximum torque is applied to the first end effectorand the second end effector to generate a maximum tip force to squeezetightly around the tissue regardless of any cable stretch in the cablesof the robotic surgical instrument. After squeezing tightly on thetissue, the method may go to block 2410 if an electro-surgicalinstrument is being used. If the robotic surgical tool is not anelectro-surgical instrument, block 2410 is skipped and the method jumpsto block 2412.

At block 2410, assuming the robotic surgical tool is an electro-surgicalinstrument and maximum torque has been applied, electrical energy issupplied to one or both of the first end effector and the second endeffector. If supplied to both, a bipolar generator is utilized with thebipolar electro-surgical tool. If supplied to one end effector, amono-polar generator is utilized with the mono-polar electro-surgicaltool. The electrical energy may be supplied to cauterize tissue or toseal tissue closed. The amount of electrical energy supplied may be afunction of the impedance of the tissue, the clamping force applied tothe tissue by the end effectors, and the time that the electrical energyis to be supplied to the end effectors. After supplying the electricalenergy, the method goes to block 2412.

At block 2412, a determination is made as to whether or not the gripshave been released to reduce the torque at the first end effector andthe second end effector. If the grips have not been released but aremaintained closed, then the maximum torque is maintained by looping backaround to block 2408 where the application of the maximum torque isrepeated. If the grips have been released, the method goes to block2414.

At block 2414, the grips have been released and the torque applied tothe first end effector and the second end effector is reduced and themethod may go to block 2499 and end. Alternatively, the portions of themethod after calibration may repeat itself over and over again until therobotic surgery is completed.

While the mounting of the tool is discussed as changing the softwaresettings for torque limited control of the servomotors, the torquelimited control of the robotic surgical tool may be selectively enabledby a switch. For example a separate actuator, such as a foot pedal, maybe pressed to enable the torque limited control and increase the gripforce to apply maximum torque to the end effectors. Alternatively, abutton, toggle switch, or momentary switch may be used to toggle betweena normal mode of driving the end effectors and a torque limited mode ofdriving the end effectors.

CONCLUSION

The embodiments of the invention provide for consistently driving endeffectors of a robotic surgical instrument to attain maximum grippingforce (torque) throughout its lifetime, regardless of cable stretch.While the embodiments of invention were particularly described withrespect to electro-surgical tools, they can also be applied to othercable driven gripping instruments, such as dissecting forceps, and othertools with cable stretch where the prior control system may limitreaching maximum gripping force (torque) of the robotic surgical tool.

One or more elements in the embodiment of the invention may beimplemented in software to execute on a processor of a computer system.When implemented in software, the elements of the embodiments of theinvention are essentially the code segments to perform the necessarytasks. The program or code segments can be stored in a processorreadable medium or transmitted by a computer data signal embodied in acarrier wave over a transmission medium or communication link. The“processor readable medium” may include any medium that can store ortransfer information including an optical medium, semiconductor medium,and magnetic medium. Processor readable medium examples include anelectronic circuit; a semiconductor device, a semiconductor memorydevice, a read only memory (ROM), a flash memory, an erasableprogrammable read only memory (EPROM); a floppy diskette, a CD-ROM, anoptical disk, a hard disk, a fiber optic medium, a radio frequency (RF)link, etc. The computer data signal may include any signal that canpropagate over a transmission medium such as electronic networkchannels, optical fibers, air, electromagnetic, RF links, etc. The codesegments may be downloaded via computer networks such as the Internet,Intranet, etc.

While certain exemplary embodiments of the invention have been describedand shown in the accompanying drawings, it is to be understood that suchembodiments are merely illustrative of and not restrictive on the broadinvention, and that the embodiments of the invention not be limited tothe specific constructions and arrangements shown and described, sincevarious other modifications may occur to those ordinarily skilled in theart. For example, the embodiments of the invention were particularlydescribed with referenced to robotic electro-surgical tools but areapplicable to other robotic surgical instruments.

1-13. (canceled)
 14. A method for a robotic surgical instrumentcomprising: limiting a desired torque to a range between an upper torquelimit and a lower torque limit; transforming the desired torque into afirst current signal; and driving a first end effector to the limiteddesired torque in response to the first current signal.
 15. The methodof claim 14, further comprising: prior to driving the first endeffector, requesting a control system to position the first end effectorat a negative angle with respect to a second end effector, the secondend effector rotatably coupled to the first end effector at a firstaxis.
 16. The method of claim 14, further comprising: prior to drivingthe first end effector, transforming the desired torque into the firstcurrent signal and a second current signal; and driving the first endeffector and a second end effector to the desired torque in response tothe first current signal and the second current signal, respectively.17. The method of claim 14, wherein in transforming the desired torque,the desired torque is split and transformed into the first currentsignal and the second current signal,
 18. A method for a roboticsurgical instrument comprising: mounting the robotic surgical instrumentto a robotic surgical arm; reading a memory in the robotic surgical toolto determine a tool type and any control system adjustments; adjusting acontrol system to drive a first end effector to a torque in a rangebetween an upper torque limit and a lower torque limit; and driving thefirst end effector to the torque in the range.
 19. The method of claim18, further comprising: prior to driving the first end effector,adjusting the control system to drive a first end effector and a secondend effector to a torque in a range between an upper torque limit and alower torque limit; and driving the first end effector and the secondend effector to the torque in the range.
 20. The method of claim 18,wherein the torque is a desired joint torque at the first end effector.21. The method of claim 19, wherein the torque is a desired joint torqueat the pivot pin of the first end effector and the second end effector.22. The method of claim 18, wherein driving the first end effectorincludes driving a first drive pulley to the torque in the range thetorque is a desired joint torque at the first end effector.
 23. Themethod of claim 19, wherein driving the first end effector and thesecond end effector includes driving a first drive pulley and a seconddrive pulley to the torque in the range.
 24. A method for a roboticsurgical system comprising: calibrating a robotic surgical instrumentcoupled to a robotic surgical arm prior to a robotic surgical procedureto determine a bump point between a first end effector and a second endeffector; first squeezing grips of a touch sensitive handle to close thefirst end effector and the second end effector around tissue; secondsqueezing the grips of the touch sensitive handle to apply additionaltorque to the first end effector and the second end effector to apply atip force to the tissue; and applying a maximum torque to the first endeffector and the second end effector to apply a maximum tip force to thetissue regardless of cable stretch in the robotic surgical instrument.25. The method of claim 24, further comprising: after applying maximumtorque, supplying electrical energy to the first end effector and thesecond end effector to cauterize the tissue.
 26. The method of claim 24,further comprising: after applying maximum torque, supplying electricalenergy to the first end effector and the second end effector to seal thetissue closed.
 27. The method of claim 24, further comprising:determining if the grips have been released to reduce the torque at thefirst end effector and the second end effector, if so, then reducing thetorque to the first end effector and the second end effector, and ifnot, then repeating the applying of the maximum torque.